PURPOSE: To facilitate a brake releasing operation by providing a brake and a brake operating mechanism on the end part of the whole of a hydraulic motor mechanism and connecting both mechanisms with each other by means of a connecting rod.

CONSTITUTION: When a push plate 38 moves via a connecting rod 28, contact between a rotary braking plate 40 and a fixed braking plate 40' allowed to make close contact with each other by means of the press plate 38 is separated away, a parking brake 39 is released, and in input shaft 14 is made rotatable. Namely, when the hydraulic motor 11 is turned, it is possible to easily release the parking brake 39.