PURPOSE: To provide a compact pressure controller for an actuator which allows the operation of an artificial muscle to be able to act just as five fingers of a human being.

CONSTITUTION: While no voltage is applied between a center electrode 7 and a peripheral electrode 6, the pressure in an artificial muscle 5 changes according to a pulse pressure to be applied to an electroviscous fluid 2 in a cylinder 3. When a voltage is applied between both the electrodes by a control means, a rise in the viscosity occurs in the electroviscous fluid 2 between both the electrodes and the pressure in the cylinder 3 and the pressure in the artificial muscle 5 are cut off in substance so that the pressure in the artificial muscle 5 is maintained at a value at the moment thereafter. This enables the supplying of an arbitrary pressure to the artificial muscle 5 with a better response within a range of changes in the pressure by a pressure generation mean thereby allowing the artificial muscle to work quickly and in a versatile manner.