The present invention provides a wet type multi-plate clutch comprising a first friction engaging element coaxially arranged within a clutch housing, a second friction engaging element alternately disposed with the first friction engaging element and a piston for applying an axial load to engage the first and second friction engaging elements with each other and wherein a projection protruding toward the piston is provided on the clutch housing and a recessed portion is provided in the piston so that a relative rotation between the clutch housing and the piston is prevented by engaging the projection with the recessed portion.