A cavity 135 having a closed end wall 135a facing an end of a rotational shaft 71 and receiving the end of the rotational shaft 71 therein is defined in an inner surface of a case cover 55 such that supply oil passages 125, 126 are open at inner circumferential surfaces of the cavity 135. At least one radial joint hole 138 is defined in an end portion of the rotational shaft 71 and extends radially of the rotational shaft 71, the radial joint hole 138 having an inner end connected to another oil passage 111 in the rotational shaft 71 than a particular oil passage 112 in the rotational shaft 71. The radial joint hole 138 is connected to a corresponding supply oil passage 125 of the supply oil passages 125, 126, in the cavity 135.