A speed change device where the plurality of oil holes have a plurality of first oil holes that are closest to the piston in the axial direction and that are disposed side by side in a circumferential direction, and a plurality of different oil holes that are farther from the piston than the plurality of first oil holes in the axial direction, the plurality of oil holes enabling the working oil to be supplied to spaces between the plurality of inner friction plates and the outer friction plates; and a number of the plurality of different oil holes is smaller than a number of the plurality of first oil holes, the plurality of different oil holes being disposed side by side in the circumferential direction at a position that is farther from the piston than the plurality of first oil holes in the axial direction.