The rotary damper comprises: case having viscous fluid 13 filled cylindrical chamber; rotor housed in the chamber; check valve; and pressure-regulating valve. In the chamber, projecting bulkheads are formed. The rotor comprises: the rotor body and vanes. The check valve closes when the rotor rotates in the normal rotation direction, so as to restrict movement of the viscous fluid between areas 111a-111d partitioned by the bulkheads and the vanes. On the other hand, the check valve opens when the rotor rotates in the reverse rotation direction, so as to allow movement of the viscous fluid between the areas 111a-111d. The pressure-regulating valve opens when rotating force applied for rotating the rotor in the normal rotation direction is above a predetermined value, to cancel the restriction of movement of the viscous fluid between the areas 111a-111d.