In an engine unit, a drive unit case includes a crank shaft disposed in a left-right direction of a vehicle, a drive shaft and a second main shaft. A transmission shaft is parallel or substantially parallel to the drive shaft and transmits rotational power, which has been transmitted via a middle gear, to a propeller shaft. A second clutch, which transmits rotational power from the crank shaft to the second main shaft, is freely detachably connected to an end of one side of the second main shaft which protrudes from a drive unit case more than the end of one side of the drive shaft, at a position that overlaps with at least one section of the middle gear on the side of the shaft direction of the drive shaft.