Power transmission device and working vehicle

A power transmission device that drives a wheel of a working vehicle includes a motor having a rotor for extracting rotation output, and a stator around which a coil for forming a magnetic field is wound; and a brake mechanism that brakes the rotation of a shaft that rotates integrally with the rotor. The brake mechanism includes a multiplate type braking part composed of a plurality of friction plates, and some of the friction plates may be stored radially inside a coil end of the coil.