To improve durability of a one-way clutch, in the one-way clutch formed such that the one-way clutch 2 situated in juxtaposition with a hydraulic friction element 1 is coupled to each of an inner member 10 and an outer member 11 of the hydraulic friction element 1, the clutch consists of a plate type one-way clutch provided with first and second plates 20 and 21, axially opposed to each other, and relative rotation in one-way direction of the first plate is allowed, however, relative rotation in the other direction of the first plate is blocked as a result of a claw piece 24 mounted on a pocket part 22 of the first plate being engaged with a notch part of the second plate.

The first plate 20 is formed integrally with the inner member 10. An input part for restraining torque inputted to the first plate 20 through the claw piece 24 is reinforced by the inner member 10 and durability is improved.