A friction clutch includes a clutch housing having a friction plate, a clutch boss having a clutch plate, a pressure plate, a sub clutch, and a power-assist mechanism. An elastic member urges the pressure plate in a predetermined direction to press the friction plate and the clutch plate into frictional contact with each other when the clutch is engaged. The sub clutch includes a friction plate operatively disposed between first and second pressing plates. The power-assist mechanism receives torque from the pressure plate via the sub clutch when the clutch is disengaged and converts the torque into a force for moving the pressure plate in a direction which separates the pressure plate from a plate group.