To sufficiently shorten the length of an output shaft in a structure for installing a fluid type retarder on the output shaft of a transmission.

This fluid type retarder 2 is installed on the output shaft 28 of the transmission in a motive power transmission system including the transmission and a propeller shaft. The fluid type retarder 2 has an output flange 29, a stator 25, a rotor 24 and a hydraulic fluid supply device. The output flange 29 is relatively nonrotatably installed on an outer peripheral surface of the output shaft 28, and outputs motive power to the propeller shaft. The rotor 24 is relatively nonrotatably installed on an outer peripheral surface of the output flange 29. The stator 25 is oppositely arranged to the rotor 24. The hydraulic fluid supply device is a device for supplying a hydraulic fluid to a space between the rotor 24 and the stator 25.