PURPOSE: To make a braking device compact and lightweight to facilitate repair and assembling operation of it by making the angular speed of rotation of a shaft to be braked faster than the angular speed of rotation of a rotating member.

CONSTITUTION: When a vehicle is braked, a braking pressurizing fluid is fed to a cylinder device to hold a braking side circular disc 16 and a braked side circular disc 17 in the axial direction of a housing 30. As a result, frictional force acts between the side faces of both the circular discs 16, 17, and the rotating speed of the braked side circular disc 17 is liable to decrease by braking torque based on the frictional force. In this case, by the use of a transmission device for making the angular speed of rotation of a shaft to be braked faster than the angular speed of rotation of a rotating member, the braked side circular disc 17 is rotated at higher speed than wheels 28. Thus, the braking torque applied to the wheels 28 becomes greater than the braking force applied to the braked side circular disc 17. Consequently, a sufficient large braking torque can be obtained without making a braking device 29 large-size.