A rotation transmission device comprising: an input shaft; an output shaft arranged so as to be coaxial with the input shaft; a housing covering ends of the input shaft and the output shaft; a two-way clutch mounted in the housing and configured to selectively permit and prohibit transmission of rotation from the input shaft to the output shaft; and an electromagnetic clutch provided on the input shaft, and configured to selectively engage and disengage the two-way clutch, wherein the electromagnetic clutch comprises: an armature supported so as to be movable in an axial direction of the input shaft; a rotor including an inner tubular portion and an outer tubular portion provided outwardly of the inner tubular portion and different in diameter from the inner tubular portion, the inner tubular portion being fitted on the input shaft, and positioned in the axial direction, while being opposed to the armature; and an electromagnet mounted between the outer tubular portion and the inner tubular portion of the rotor so as to be opposed to the rotor in the axial direction, and configured to apply a magnetic attraction force to the armature that tends to attract the armature to the rotor, when the electromagnet is energized, the electromagnet including an electromagnetic coil and a core supporting the electromagnetic coil, a bearing, wherein the rotation transmission device is configured such that when the electromagnet is energized, the armature is moved in the axial direction toward the rotor, thereby disengaging the two-way clutch, characterized in that the rotation transmission device comprises a bearing support tube, wherein the bearing support tube is provided at an outer end surface of the core; a small-diameter tubular portion is provided at an end of the inner tubular portion of the rotor and located radially inside the bearing support tube; the bearing is mounted radially inside the bearing support tube; and the small-diameter tubular portion is press-fitted into the bearing such that the electromagnet and the rotor form a unit. an input shaft; an output shaft arranged so as to be coaxial with the input shaft; a housing covering ends of the input shaft and the output shaft; a two-way clutch mounted in the housing and configured to selectively permit and prohibit transmission of rotation from the input shaft to the output shaft; and an electromagnetic clutch provided on the input shaft, and configured to selectively engage and disengage the two-way clutch, wherein the electromagnetic clutch comprises: an armature supported so as to be movable in an axial direction of the input shaft; a rotor including an inner tubular portion and an outer tubular portion provided outwardly of the inner tubular portion and different in diameter from the inner tubular portion, the inner tubular portion being fitted on the input shaft, and positioned in the axial direction, while being opposed to the armature; and an electromagnet mounted between the outer tubular portion and the inner tubular portion of the rotor so as to be opposed to the rotor in the axial direction, and configured to apply a magnetic attraction force to the armature that tends to attract the armature to the rotor, when the electromagnet is energized, the electromagnet including an electromagnetic coil and a core supporting the electromagnetic coil, an armature supported so as to be movable in an axial direction of the input shaft; a rotor including an inner tubular portion and an outer tubular portion provided outwardly of the inner tubular portion and different in diameter from the inner tubular portion, the inner tubular portion being fitted on the input shaft, and positioned in the axial direction, while being opposed to the armature; and an electromagnet mounted between the outer tubular portion and the inner tubular portion of the rotor so as to be opposed to the rotor in the axial direction, and configured to apply a magnetic attraction force to the armature that tends to attract the armature to the rotor, when the electromagnet is energized, the electromagnet including an electromagnetic coil and a core supporting the electromagnetic coil, a bearing, wherein the rotation transmission device is configured such that when the electromagnet is energized, the armature is moved in the axial direction toward the rotor, thereby disengaging the two-way clutch, characterized in that the rotation transmission device comprises a bearing support tube, wherein the bearing support tube is provided at an outer end surface of the core; a small-diameter tubular portion is provided at an end of the inner tubular portion of the rotor and located radially inside the bearing support tube; the bearing is mounted radially inside the bearing support tube; and the small-diameter tubular portion is press-fitted into the bearing such that the electromagnet and the rotor form a unit.