A reverse input blocking clutch, comprising: a pressed member having a cylindrical concave-shaped pressed surface having a center axis; an input member having an input engaging portion arranged on an inner side in a radial direction of the pressed surface and having a center axis of rotation that is coaxial with the central axis of the pressed surface; an output member having an output engaging portion arranged further on the inner side in the radial direction of the pressed surface than the input engaging portion and having a center axis of rotation that is coaxial with the pressed surface; and an engaging member having a first portion arranged on the inner side in the radial direction of the pressed surface at a position located in the radial direction between the input engaging portion and the output engaging portion, and a pair of second portions arranged at positions on both sides in a circumferential direction from the position located in the radial direction between the input engaging portion and the output engaging portion; the engaging member being configured so that in a case where rotational torque is inputted to the input member, the engaging member moves in a direction away from the pressed surface due to the input engaging portion engaging with the first portion, and by the first portion engaging with the output engaging portion, transmits the rotational torque that is inputted to the input member to the output member; and in a case where rotational torque is reversely inputted to the output member, the engaging member moves in a direction toward the pressed surface due to the output engaging portion engaging with the first portion, and by the pair of second portions being pressed against the pressed surface, does not transmit the rotational torque that is reversely inputted to the output member to the input member, or transmits a part of the rotational torque that is reversely inputted to the output member, to the input member, and blocks a remaining part thereof; characterized in that in a case where rotational torque is reversely inputted to the output member, a pair of contact portions (M1, M2) where the pair of second portions and the pressed surface come in contact are positioned on sides closer to the center axis of the pressed surface than a specified portion with respect to a direction of a bisector of tangent lines (X1, X2) of the pressed surface at each contact portion of the pair of contact portions (M1, M2), the specified portion being a portion of the first portion with which the input engaging portion engages when a rotational torque is input to the input member, and an intermediate member is arranged in a portion between the pair of second portions and the pressed member, the intermediate member being composed of a gap adjusting member that is held by the pressed member and has the pressed surface. a pressed member having a cylindrical concave-shaped pressed surface having a center axis; an input member having an input engaging portion arranged on an inner side in a radial direction of the pressed surface and having a center axis of rotation that is coaxial with the central axis of the pressed surface; an output member having an output engaging portion arranged further on the inner side in the radial direction of the pressed surface than the input engaging portion and having a center axis of rotation that is coaxial with the pressed surface; and an engaging member having a first portion arranged on the inner side in the radial direction of the pressed surface at a position located in the radial direction between the input engaging portion and the output engaging portion, and a pair of second portions arranged at positions on both sides in a circumferential direction from the position located in the radial direction between the input engaging portion and the output engaging portion; the engaging member being configured so that in a case where rotational torque is inputted to the input member, the engaging member moves in a direction away from the pressed surface due to the input engaging portion engaging with the first portion, and by the first portion engaging with the output engaging portion, transmits the rotational torque that is inputted to the input member to the output member; and in a case where rotational torque is reversely inputted to the output member, the engaging member moves in a direction toward the pressed surface due to the output engaging portion engaging with the first portion, and by the pair of second portions being pressed against the pressed surface, does not transmit the rotational torque that is reversely inputted to the output member to the input member, or transmits a part of the rotational torque that is reversely inputted to the output member, to the input member, and blocks a remaining part thereof; characterized in that in a case where rotational torque is reversely inputted to the output member, a pair of contact portions (M1, M2) where the pair of second portions and the pressed surface come in contact are positioned on sides closer to the center axis of the pressed surface than a specified portion with respect to a direction of a bisector of tangent lines (X1, X2) of the pressed surface at each contact portion of the pair of contact portions (M1, M2), the specified portion being a portion of the first portion with which the input engaging portion engages when a rotational torque is input to the input member, and an intermediate member is arranged in a portion between the pair of second portions and the pressed member, the intermediate member being composed of a gap adjusting member that is held by the pressed member and has the pressed surface.