PURPOSE: To quickly generate damping force and thereby lessen delay in response by making up an orifice out of a throttle hole formed in a switch-over valve, and of a needle valve which is fixed on the wall of an auxiliary oil chamber which is faced to the throttle hole while being extended into the throttle hole.

CONSTITUTION: An orifice 72 which mutually connects a first and a second auxiliary oil chamber 68 and 70, is made up out of a throttle hole 72a formed in a switch-over valve 66, and a needle valve 72b which is fixed on the wall of the first auxiliary oil chamber 68 faced to the switch-over valve. The switch-over valve 66 quickly starts moving with the pressure of the first auxiliary oil chamber 65 quickly increased. This thereby causes the pressure of the second auxiliary oil chamber 70 to be increased, and consequently causes a plunger 82 to be pressed down, so that oil in the second auxiliary oil chamber 70 to run away to a lower pressure side main oil chamber 54 while speeds are lowered therein. When the opening of the orifice 72 is increased in area with the switch-over valve 66 lowered down, the difference in pressure between the first and the second auxiliary oil chamber 68 and 70 is abruptly decreased, so that the switch-over valve 66 is thereby quickly restored. By this constitution, damping force is quickly generated, and delay in response is thereby lessened.