PURPOSE: To have a rotary damper device used for applying a resistance to a rotating body for damping any shock exerted thereon, so that the device may exhibit its large resistance force regardless of its small size and particularly it can possess its smooth operation characteristics.

CONSTITUTION: Projecting external teeth 3 are provided in the central part of a circular chamber 1, and an internal teeth 5 to rotate while meshing with the external teeth 3 are arranged in a rotor 6, and by setting the number of teeth of the internal teeth 5 more than the number of the external teeth 3 by one piece, the rotor 6 can rotate eccentrically around the external teeth 3, and in that case, a viscous agent 10 filled in a meshing space 11 between the internal and the external teeth moves in the space so that resistance can be generated, and a rotation input part 8 such as a rotary shaft is also arranged in a rotary member 9 having an eccentric chamber 7 to rotate the rotor 6 eccentrically in the circular chamber.