A power transmission device for an electrically driven vehicle basically includes a power transmission mechanism, a sliding contact brush, a brush case cover, and a brush protective jig. The power transmission mechanism includes a case element, an axle element and a power transmission element. The sliding contact brush is mounted on an axle end of the axle element. The brush case cover is selectively mounted to the case element to enclose the axle end of the axle element in the case element. The brush protective jig is mounted to cover the brush contact when mounting the sliding contact brush to the axle end. The brush protective jig is dimensioned to contact the brush case cover and to prevent the brush case cover from being mounted to the case element while the brush protective jig is in an attached state that covers the brush contact.