PURPOSE: To enhance the noise reducing effect in a low-speed region by providing a plunger with a passage for releasing the fuel inside a high-pressure chamber into a low-pressure chamber in the low-speed region, and also by providing this releasing passage with an orifice.

CONSTITUTION: At the time of low-speed operation of an engine, the fuel inside a high-pressure chamber 911 leaks into a low-pressure chamber 90 through a releasing passage 1 of a plunger 92. Consequently, pressure-rising performance is lessened, and the start of injection is delayed. On the other hand, at the time of high-speed operation of the engine, there is almost no leakage of fuel through the releasing passage 1 due to the orifice effect of the orifice 10 that has been provided in the releasing passage 1. Accordingly, there is little difference in the start of injection as compared with the case where the releasing passage 1 is not provided. Therefore, the difference between the can turning angle in the start of injection at the time of low-speed operation and that in the start of injection at the time of high-speed operation can be reduced. Thus, the width of the advance angle of a timer can be reduced.