To provide a fluid type retarder device having a quite simple structure in which a thrust force can be reduced only through an arrangement of sealing sections having different diameters at a front surface and a rear surface of a rotor.

A fluid type retarder device in which fluid discharged from a stator is received by a rotor 6 facing against a stator 1c to apply a brake against a rotating shaft 5 is constructed such that there are provided a stator 1c arranged at a stopped housing 1 and a rotor 6 fixed to a rotating shaft 5 rotatable to pass through the housing 1, sealed against the housing 1 at a predetermined position in a direction of diameter at the surface of the rotor 6, sealed at a position lower than a predetermined position at the surface of the rotor 6 at an opposing surface of the rotor 6 so as to increase a pressure receiving area than that of the rotor.