Vehicle provided with a supercharger-equipped combustion engine mounted on the vehicle and comprising: an engine rotary shaft extending in a widthwise direction of the vehicle; a crankcase supporting the engine rotary shaft and including a crankcase body having an opening formed so as to be opened at one side in the widthwise direction of the vehicle; a supercharger disposed above the crankcase with respect to the vertical direction of the vehicle, and configured to pressurize and then discharge intake air; a power transmission mechanism configured to transmit power from the engine rotary shaft to the supercharger, wherein the power transmission mechanism includes a power transmission shaft unit (78, 82) extending in the widthwise direction of the vehicle, the power transmission shaft unit (78, 82) is supported at a first end portion (78a, 82a) thereof at the one side and at a second end portion (78b, 82b) thereof at the other side in the widthwise direction of the vehicle; characterized by comprising: a holder, covering at least a part of the opening of the crankcase body from the one side in the widthwise direction of the vehicle and detachably mounted on the crankcase body, a first bearing portion (43a, 43b) formed in the holder, rotatably supporting the first end portion (78a, 82a) of the power transmission shaft unit (78, 82), and a second bearing portion (41a, 41b) formed in a side wall of the crankcase, rotatably supporting the second end portion (78b, 82b) of the power transmission shaft unit (78, 82); wherein the power transmission shaft unit (78, 82) includes first and second rotary shafts (78, 82) respectively supporting a pair of gears (92A, 96A; 94A, 98A) which mesh with each other, each of the first and second rotary shafts (78, 82) has the first end portion (78a, 82a) and the second end portion (78b, 82b), the first bearing portion (43a, 43b) formed in the holder supports the first end portions (78a, 82a) of the first and second rotary shafts (78, 82), and the second bearing portion (41a, 41b) formed in the side wall of the crankcase supports the second end portions (78b, 82b) of the first and second rotary shafts (78, 82). an engine rotary shaft extending in a widthwise direction of the vehicle; a crankcase supporting the engine rotary shaft and including a crankcase body having an opening formed so as to be opened at one side in the widthwise direction of the vehicle; a supercharger disposed above the crankcase with respect to the vertical direction of the vehicle, and configured to pressurize and then discharge intake air; a power transmission mechanism configured to transmit power from the engine rotary shaft to the supercharger, wherein the power transmission mechanism includes a power transmission shaft unit (78, 82) extending in the widthwise direction of the vehicle, the power transmission shaft unit (78, 82) is supported at a first end portion (78a, 82a) thereof at the one side and at a second end portion (78b, 82b) thereof at the other side in the widthwise direction of the vehicle; a holder, covering at least a part of the opening of the crankcase body from the one side in the widthwise direction of the vehicle and detachably mounted on the crankcase body, a first bearing portion (43a, 43b) formed in the holder, rotatably supporting the first end portion (78a, 82a) of the power transmission shaft unit (78, 82), and a second bearing portion (41a, 41b) formed in a side wall of the crankcase, rotatably supporting the second end portion (78b, 82b) of the power transmission shaft unit (78, 82);