To adjust torque after a damper is assembled and change the torque loosely without a risk of viscous fluid's leaking or the torque's changing after adjustment.

This damper comprises viscous fluid V stored in a casing 10 whose inner surface is equipped with a projected part, a rotary member 30 whose part is stored in the casing 10, and an annular cap 20 with which the opening of a casing is covered, and a valve element 32 is engaged with the projected groove 15 arranged to the outer surface of the rotary member 30 in the casing 10 so as to change flow resistance by rotating the rotary member 30 in normal and reverse directions. In this case, an adjusting ring 40 by which the axial position of the rotary member 30 is regulated to be adjusted through the annular cap 20 is arranged to the opening of the casing.