An axle of an industrial vehicle, in which a parking brake can be maintained easily. The parking brake is arranged adjacent to a power transmission device outside an axle housing. The parking brake includes a brake housing, a brake shaft supported rotatably around the axis of the brake housing, a brake gear attached to the brake shaft and meshed with a transmission gear, first brake plates attached to the brake shaft, second brake plates attached to the brake housing and alternately arranged with the first brake plates, and a brake piston arranged so as to move toward and away from the plates and in the brake housing for bringing the plates into pressure contact with each other.