A fuel injection pump, comprising three sub-mechanism parts; a lower mechanism part (A), a head mechanism part (B), and a governor mechanism part (C), wherein, when the governor mechanism part (C) is assembled into the combination of the lower mechanism part (A) and head mechanism part (B) after the lower mechanism part (A) and head mechanism part (B) are assembled with each other, a governor link (27) installed extendedly from the governor mechanism part (C) is inserted into both mechanism parts (A, B) and, when a hook groove (27a) at the tip of the governor link (27) is engaged with a lock pin (21a) in a control slider (21) for the rotation of a plunger (7) disposed inside the lower mechanism part (A) and head mechanism part (B), first, with a notch surface (33b) of a lift pin (33) facing upward, the governor link (27) is put on the notch surface (33b) so as to position the hook groove (27a) under the lock pin (21a), and then the lift pin (33) is rotated to face the notch surface (33b) downward, and the governor link (27) is swung upward by a cam part (33a) so as to engage the hook groove (27a) with the lock pin (21a).