PURPOSE: To improve durability by reducing vibration applied to a rotation sensor, and control injection quantity and injection timing correctly.

CONSTITUTION: In an injection pump 20, a rotor 33 which rotates integrally with a drive shaft 38 is provided with a plunger 35 to slide diametrically, and a cam ring 37 to actuate the plunger 35 is provided at an outer circumference of the rotor 33. A rotation angle position is detected by a pulser 56 fixed to a large diameter part 33a of the rotor 33 and a rotation sensor 55 fixed to the cam ring 37. A slide pin 66 of a timer part 65 disposed at an outer circumferential part of the cam ring 37 slides the cam ring 37 along the circumference to regulate fuel injection timing. The rotation sensor 55 is disposed almost at the same position in the circumference of the cam ring 37 to the slide pin 66. A distance between the rotation sensor 55 and the slide pin 66 is thus set short, thereby vibration of the rotation sensor is reduced.