This fluid-type retarding device includes: a rotating disk provided to a rotating shaft; a rotating housing that includes paired disk portions and a cylinder portion connecting outer circumferential portions of the disk portions so as to surround the rotating disk, and is rotatably supported with the rotating shaft; and a friction brake that presses a friction member against the rotating housing at the time of braking to bring the rotating housing to a stop. On at least one surface of the rotating disk, a disk vane extending from an inner circumference of the surface toward an outer peripheral side is formed, and on an inner surface of each of the paired disk portions corresponding to the disk vane, a housing vane extending from an inner circumference to an outer periphery is formed. Furthermore, working fluid is accommodated within the rotating housing.