A power transmission device comprising: a clutch housing that rotates together with rotation of an input member and to which a plurality of drive-side clutch plates are attached; a clutch member to which a plurality of driven-side clutch plates that are formed alternately with the drive-side clutch plates of the clutch housing are attached and to which an output member is coupled; a pressure member that is attached to the clutch member and that is capable of pressing the drive-side clutch plates and the driven-side clutch plates against each other or releasing a press-contact force in accordance with movement thereof relative to the clutch member in an axial direction; urging means that urges the pressure member in a direction such that the drive-side clutch plates and the driven-side clutch plates are pressed against each other; activation means that is activated by an operation performed by a driver and that is capable of releasing a press-contact force between the drive-side clutch plates and the driven-side clutch plates by moving the pressure member against an urging force of the urging means; and a back-torque limiting cam that is constituted by a pair of cam surfaces that reduce the press-contact force between the drive-side clutch plates and the driven-side clutch plates if the pressure member and the clutch member rotate relative to each other when a rotation speed of the output member exceeds a rotation speed of the input member, wherein the power transmission device is capable of transmitting or cutting off rotational power that is input to the input member to the output member by pressing the drive-side clutch plates and the driven-side clutch plates against each other or releasing the press-contact force, characterized in that the power transmission device includes a rotation restricting portion that is capable of restricting rotation, relative to the clutch member, of the pressure member that has moved due to activation of the activation means and is capable of maintaining a clearance between the pair of cam surfaces that constitute the back-torque limiting cam, and in that the power transmission device comprises a fixing member that is fixed to the clutch member and to which the urging means is attached, wherein the rotation restricting portion is formed in a predetermined part of the fixing member. a clutch housing that rotates together with rotation of an input member and to which a plurality of drive-side clutch plates are attached; a clutch member to which a plurality of driven-side clutch plates that are formed alternately with the drive-side clutch plates of the clutch housing are attached and to which an output member is coupled; a pressure member that is attached to the clutch member and that is capable of pressing the drive-side clutch plates and the driven-side clutch plates against each other or releasing a press-contact force in accordance with movement thereof relative to the clutch member in an axial direction; urging means that urges the pressure member in a direction such that the drive-side clutch plates and the driven-side clutch plates are pressed against each other; activation means that is activated by an operation performed by a driver and that is capable of releasing a press-contact force between the drive-side clutch plates and the driven-side clutch plates by moving the pressure member against an urging force of the urging means; and a back-torque limiting cam that is constituted by a pair of cam surfaces that reduce the press-contact force between the drive-side clutch plates and the driven-side clutch plates if the pressure member and the clutch member rotate relative to each other when a rotation speed of the output member exceeds a rotation speed of the input member, wherein the power transmission device is capable of transmitting or cutting off rotational power that is input to the input member to the output member by pressing the drive-side clutch plates and the driven-side clutch plates against each other or releasing the press-contact force, characterized in that the power transmission device includes a rotation restricting portion that is capable of restricting rotation, relative to the clutch member, of the pressure member that has moved due to activation of the activation means and is capable of maintaining a clearance between the pair of cam surfaces that constitute the back-torque limiting cam, and in that the power transmission device comprises a fixing member that is fixed to the clutch member and to which the urging means is attached, wherein the rotation restricting portion is formed in a predetermined part of the fixing member.