A milk expressing device capable of simulating a babys suckling includes first and second vacuum sources, a throttle hole, a solenoid relief valve, first and second tubes, a breast shield, and a control circuit board. The first tube connecting the first vacuum source and the breast shield is provided with the throttle hole to communicate with the atmosphere. When the first vacuum source is turned off, negative pressure in the first tube and the breast shield disappears slowly through the throttle hole. The second tube connecting the second vacuum source and the breast shield is provided with the solenoid relief valve to communicate with the atmosphere. When the solenoid relief valve is activated, negative pressure in the second tube and in the breast shield is rapidly removed. The control circuit board controls the first and second vacuum sources and the solenoid relief valve.
