A high pressure fuel supply pump comprises a cylinder, the upper part of which is exposed to the outside of a head cover that is a part of the engine housing, and is fixed to the head cover by means of bolts, not shown. The remaining portion of the high pressure fuel supply pump is received in an accommodation hole of the head cover. A pump cam 111 is mounted to a valve camshaft for driving a suction/exhaust valve and drives the high pressure fuel supply pump. The use of an exclusive shaft for pump driving only, a bearing member therefor, and the like is rendered unnecessary, which enables a reduction in the number of parts employed. Further, since the timing with which the pressurized fuel is discharged is controlled through the operation of a solenoid valve, the precision with which fuel injection is controlled is improved.