PURPOSE: To facilitate the machining of a fuel injection pump and to reduce the entire length of the same, by forming fuel metering chambers for storing fuel temporarily in a section of a hydraulic head extending perpendicularly to the axis of rotation of the fuel injection pump.

CONSTITUTION: Second pump chambers 26 are formed between the outer peripheral surface of a rotor 1 and the inner surface of a sleeve 4. Fuel passages extended from switching ports 13, 18 formed in the sleeve 4 to a first metering chamber 14 and a second metering chamber 19 are formed in a single section by disposing the metering chambers 14, 19 in a section extending perpendicularly to the axis of rotation of a pump. Therefore, the structure of fuel passages can be simplified. Further, since the length and the travelling distance of a first and a second pistons 15, 20 can be reduced and the length of the inner surface of a hydraulic head 6 and the length of the outer surface of the rotor 1 to be machined can be also reduced, it is enabled to facilitate machining of the pump.