PURPOSE: To deliver oil at constant pressure for reduction in the delivering pulsation of pressure oil by transmitting the oil pressure reversely to a pressure- raising part in response to the oil pressure raised at the pressure-raising part, and proportionally-controlling the delivery pressure of oil by an automatic exhaust-control valve.

CONSTITUTION: When an electromagnetic pump 100 elevates a plunger combination 151 using magnetic force by energizing the solenoid 154 of the operating part 131 at a pressure-raising part 130, an inlet check valve 132 is opened, so that oil flows into the second passage 162 from an oil tank 112. When the plunger combination 151 is dropped by a spring 157 by interrupting the energizing of the solenoid 154, oil is pressurized with the opening of a deliver check- valve 134 and flown into the upper space of the plunger combination 151 through a flow passage 164, and then oil is delivered at a delivery part 140. Repeating these operations raises the pressure in a flow passage 165, by which the opening of an exhaust-control valve 200 is adjusted.