To provide a one-way clutch which prevents fatigue rupture due to stress concentration inside a pocket formed in an outer ring to improve durability.

The one-way clutch 10 includes: an inner ring 12; the outer ring 13; a recessed pocket 14 having a cam face 27 formed on the inner circumferential face of this outer ring 13 and also forming a wedge-shaped space 26 between the inner circumferential face of the outer ring 13 and the outer circumferential face of the inner ring 12; and a cylindrical roller 15 stored in the wedge-shaped space 26. Further, the one-way clutch 10 includes an initial stress imposing means which imposes initial stress resisting stress generated inside the pocket 14 by a load that the cam face 27 receives from the cylindrical roller 15 on the predetermined site of the outer ring 13 when the cylindrical roller 15 moves in the narrowing direction of the wedge-shaped space 26.