In a pump apparatus having a reduction chamber for reducing pulsation of a hydraulic fluid pressurized in a pump section on the way of a discharge channel having an opening in the outer surface of the housing of the pump section, a remaining fluid inflow prevention pipe having one end fitted into and fixed to the discharge channel between the outer surface and the reduction chamber and the other end positioned in the reduction chamber is provided, and a seal lip for fluid-tightly sealing the space between the inner wall of the discharge channel and the one end is provided on the outer circumference of the one end. The seal lip is formed in a shape tapered toward the discharge side. Further, the outside diameter of the other end of the remaining fluid inflow prevention pipe is made larger than the inside diameter of the discharge channel.