To reduce manufacturing cost and weight by improving the structure of an input-side member into which torque is input, in a clutch unit built in a seat adjuster.

The input-side member 1 having a cam surface 1Aa constituting a clutch part and a mounting part mounted with an operating lever 6 for inputting torque comprises a relatively nonrotatable combination of a first thin-walled member 1A with the cam surface 1Aa and a second thin-walled member 1B with fitting jaws 1Ba mounted with the operating lever 6. At least either of the first thin-walled member 1A and the second thin-walled member 1B is a pressed molding. Both members 1A and 1B are coupled in an interdigitated structure. At least the cam surface 1Aa of the first thin-walled member 1A is subjected to surface hardening.