A damper includes a housing having a cylindrical shape and filled with a viscous fluid, a first rotor rotatably received in the housing and having a first connecting portion formed at an end portion thereof, and a second rotor rotatably housed in the housing coaxially with the first rotor and having a second connecting portion formed at an end portion thereof. The first and second connecting portions engage to allow the first and second rotors together, and forms a space therebetween to allow the viscous fluid to pass therethrough. An elastic member urges the first connecting portion and the second connecting portion to connect together, and accumulates an elastic force in a state that the connection between the first and second connecting portions is released.