Fuel injection pump having filter

A fuel injection pump (4) includes a cam (44) rotating with a camshaft (11), a cam ring (45) revolving around the camshaft (11), a housing (30), plungers (41, 42) for pressurizing and pressure-feeding fuel drawn into fuel pressurizing chambers (51, 52), and a rotary pump (12) for supplying the fuel to the fuel pressurizing chambers (51, 52). The housing (30) includes a first housing portion (30a) for rotatably housing the rotary pump (12) and second housing portions (33, 34) for housing the plungers (41, 42) so that the plungers (41, 42) can reciprocate. A filter (81, 82) is disposed in one of an outlet portion (16bo) of a first low-pressure fuel passage (16a, 16b, 17a, 17b) in the first housing (30a) streaming the fuel from the rotary pump (12) toward the fuel pressurizing chamber (51, 52), an inlet portion of a second low-pressure fuel passage (20) of the second housing portion (33, 34) facing the outlet portion (16bo) and a certain point in the second low-pressure fuel passage (20).