To provide a roller clutch which surely realizes an over-running state even in the case where it is used for a rotation transmitting portion between two members rotating at a high speed.

A roller 3 is so restricted that a predetermined wedge angle αsatisfies the relationship α>2 tan-1(0.3). The wadge angle α is determined in the state that the roller 3 is clamped between a circumferential end of a concave portion 9a of a cam surface 8a provided on an outer periphery of an inner race 22 and an inner surface of an outer race 23. Thereby, even if the roller 3 is urged to one end portion of the concave portion 9a, the roller 3 will not bitte in the form of a wedge between the inner periphery of the outer race 23 and the outer periphery of the inner race 22.