Abstract: A power transmitting apparatus can include a gear-stage clutch comprising alternately arranged driving clutch discs and driven clutch discs; hydraulic chambers for actuating a hydraulic piston; and hydraulic oil supplying ports communicating with oil passages opening on the side surface of the input shaft for supplying the hydraulic chambers with hydraulic oil from the oil passages to actuate the hydraulic piston. Power can be transmitted at a predetermined gear ratio by engaging clutch discs of the gear-stage clutch by selectively supplying the hydraulic chambers with hydraulic oil. An annular sealing member can be fitted in a recessed portion formed around each opening of the hydraulic oil supplying port on the outer circumference of the input shaft. The recessed portion can have a flattened bottom surface on which the sealing member is seated so that it is contacted with the flattened bottom surface of the recessed portion.