A damper device includes a housing; a viscous fluid filled inside the housing; a rotor rotatably disposed inside the housing; and a sealing member for preventing the viscous fluid from leaking through the rotor and the housing. A rotational wing with a viscous-fluid passage is provided on one of the housing and the rotor. The rotational wing moves relative to the viscous fluid in a circumferential direction, and extends in a radial direction for dividing a housing portion of the housing filled with the viscous fluid. A valve is provided on the rotational wing, and is formed of an elastic member capable of deforming elastically. The valve opens the viscous-fluid passage when the rotor rotates in one direction, and blocks the viscous-fluid passage when the rotor rotates in the other direction.