To provide a rotary damper for a vehicle seat that enables a backrest to manually rotate lightly without being affected by a turning effort generated by empty weight of a backrest and further in which a function of a spiral spring can be reliably obtained.

A rotary damper 1 for a vehicle seat includes a housing 3; a rotor 7 rotatably arranged with respect to the housing 3; a vane means 8 arranged in a space 6; and a spiral spring 14 arranged on a side of a seat 11 and a backrest 13 of a vehicular seat 10 with respect to the rotor 7, where the spiral spring is connected to the seat 11 of the vehicular seat 10 at one end 9 thereof and is connected to a rotary shaft 51 fixed to the backrest 13 of the vehicular seat at the other end 12 thereof.