A wet type clutch which has its piston moved by the difference of the pressure in two oil chambers at the two sides of the piston while shutting the communication between the two oil chambers with a friction member adhered to either of the piston or a front cover to be engaged by the piston. An annular groove for communicating with such one of the two oil chambers as will take a lower pressure when the clutch is applied is formed in the surface, to which the friction member is adhered, and/or the adhered surface of the friction member itself, to reduce the pressure acting to return the piston. A seal or high porosity material may also be used to reduce the oil pressure acting on the piston.