To detect a clutch slip, while a driven body is at a stopped state, through a low cost constitution.

The clutch slip detection device is provided with a rotating sensor 13 for detecting the rotation of the driven side rotating body 12 on a slide door 1 side, in a meshing clutch 9 provided between a motor 7 and a slide door 1, in which a control unit 8 is provided with a speed calculation part 14a for calculating the actual speed (movement) of the slide door based on a pulse signal P output by the rotating sensor 13, and a slip detection part 14b which decides a clutch to be slipping when the rotational speed the actual speed of which is more than a predetermined value exceeds a specified value, and the predetermined value is set as a threshold value capable of detecting a momentary high speed when a driven side rotating body is flipped and the actual speed and the predetermined value are compared with each other to detect the clutch slip. The clutch slip can be detected with only the rotating sensor on a second member side, with simplification of the device and a reduction in cost.