A power transmission mechanism comprising left and right drive shafts (3R, 3L) that transmit rotational torque from a drive source to drive wheels provided on left and right sides of a vehicle, wherein the left and right drive shafts (3R, 3L) include an intermediate shaft (4L, 4R), a fixed type constant velocity universal joint (5L, 5R) connected to an end of the intermediate shaft (4L, 4R) on a drive wheel side, and a plunging type constant velocity universal joint (6L, 6R) connected to an end of the intermediate shaft (4L, 4R) on a side opposite to the drive wheel side, the plunging type constant velocity universal joint (6L, 6R) includes an outer joint member (21, 31) in which a track groove (21a, 31a) is formed on an inner peripheral surface, a rolling element (23, 33) rollably arranged in the track groove (21a, 31a), and an inner joint member that transmits rotational torque through the rolling element (23, 33) while allowing angular displacement and axial displacement with respect to the outer joint member (21, 31), the fixed type constant velocity universal joint (5L, 5R) includes an outer joint member in which a track groove is formed on an inner peripheral surface, an inner joint member in which a track groove is formed on an outer peripheral surface, a rolling element that is arranged between the track groove of the outer joint member and the track groove of the inner joint member and transmits rotational torque, and a cage that holds the rolling element rollably, and in the left and right drive shafts (3R, 3L), numbers of the rolling elements (23, 33) included in the respective plunging type constant velocity universal joints (6L, 6R) are different from each other, characterized in that in the left and right drive shafts (3R, 3L), numbers of the rolling elements included in the respective fixed type constant velocity universal joints (5L, 5R) are different from each other. the left and right drive shafts (3R, 3L) include an intermediate shaft (4L, 4R), a fixed type constant velocity universal joint (5L, 5R) connected to an end of the intermediate shaft (4L, 4R) on a drive wheel side, and a plunging type constant velocity universal joint (6L, 6R) connected to an end of the intermediate shaft (4L, 4R) on a side opposite to the drive wheel side, the plunging type constant velocity universal joint (6L, 6R) includes an outer joint member (21, 31) in which a track groove (21a, 31a) is formed on an inner peripheral surface, a rolling element (23, 33) rollably arranged in the track groove (21a, 31a), and an inner joint member that transmits rotational torque through the rolling element (23, 33) while allowing angular displacement and axial displacement with respect to the outer joint member (21, 31), the fixed type constant velocity universal joint (5L, 5R) includes an outer joint member in which a track groove is formed on an inner peripheral surface, an inner joint member in which a track groove is formed on an outer peripheral surface, a rolling element that is arranged between the track groove of the outer joint member and the track groove of the inner joint member and transmits rotational torque, and a cage that holds the rolling element rollably, and in the left and right drive shafts (3R, 3L), numbers of the rolling elements (23, 33) included in the respective plunging type constant velocity universal joints (6L, 6R) are different from each other,