To provide a small-sized and low-cost clutch device.

A clutch inner 11 of the clutch device 1 which is a multiplate wet clutch is connected to a flywheel 22 of an engine while a clutch outer 12 is connected to a rotor 32 of a motor 3. A plurality of drive discs 111 and driven plates 123 are alternately interposed between the clutch inner 11 and the clutch outer 12. The drive discs 111 and the driven plates 123 are made to press-contact with each other by a biasing force of a diaphragm spring 14 to be rotated integrally, and torque transmission is performed between them. The inner end of the diaphragm spring 14 is pressed by a plunger member 18 moved by hydraulic pressure, and the connection of the clutch device 1 is released. The diaphragm spring 14 has a deflection load property of increasing a deflection load accompanied by the movement of the plunger member 18 to a direction in which the connection of the clutch device 1 is released.