In a power transmission device for a vehicle, a boss portion of a clutch guide, which is an input-side rotation member of a clutch unit, includes: a spline portion spline-connected to a small-diameter portion at one end of a center shaft which is an input shaft; and a fitting portion that extends further from the spline portion in an axial direction to contact the outer circumference of a medium-diameter portion of the center shaft. A recess functioning as a torque fuse is formed in the medium-diameter portion of the center shaft corresponding to the fitting portion. When the center shaft is severed or disconnected at the recess, the medium-diameter portion of the severed cut center shaft can still remain within the fitting portion, so that appropriate centering can be secured and stable self-propulsion of the vehicle can be secured without unwanted misalignment of the axis of rotation of the clutch.