To reduce the minimum rate of fuel supplied by a pump during pumping operation by forming the outer appearance of a cam surface so as to include a first and a second regions, and generate pressure wave which exceeds a flow-out valve by operation of a plunger under the influence of the first range.

A cam outer appearance consists of a first region 62 and a second region 64. When a roller exceeds the first region 62, a plunger is pushed inward by few rate, and low pressure wave which flows in a control valve along a passage extending to an axial direction. When a control valve is opened, pressure wave flows into a chamber bypassing a passage. Until pressure wave exceeds a chamber, the roller is moved along the first region 62, but it is not engaged with the second region 64, and the projection of a piston member is lifter up by its seat until the plunger is moved inward by engaging with the second region 64. Fuel moved by inward motion of the plunger is absorbed by motion of the piston, and thereby, pressure in the passage is not increased.