A variable oil pump (100, 200) comprising: a pump housing; an oil pump rotor housed in the pump housing and rotationally driven; an adjustment member (30, 130, 230) housed in the pump housing and that adjusts an amount of oil discharged from the oil pump rotor by being displaced under hydraulic pressure supplied to a hydraulic chamber between the pump housing and the oil pump rotor in a state where the oil pump rotor is rotatably held from an outer peripheral side; a seal member (41, 42) disposed in a portion where the adjustment member (30, 130, 230) and the pump housing face each other and that seals oil leakage to an outside of the hydraulic chamber; a seal member holding portion (34a, 35a, 134a, 234a) provided in the adjustment member (30, 130, 230) and that holds the seal member (41, 42); and an oil passage (36, 81) provided in the adjustment member (30, 130, 230) and through which the hydraulic pressure in the hydraulic chamber is drawn into the seal member holding portion (34a, 35a, 134a, 234a), wherein the seal member holding portion (34a, 35a, 134a, 234a) includes a foreign matter storage portion formed in a vicinity of the root of the seal member (41, 42) and that stores foreign matter contained in the oil drawn from the hydraulic chamber and that flows through the oil passage (36, 81), characterized in that the foreign matter storage portion is formed in the seal member holding portion (34a, 35a, 134a, 234a) so as to extend in a thickness direction of the seal member (41, 42) perpendicular to a direction in which the oil passage (36, 81) extends, and a sectional area of the foreign matter storage portion in a direction perpendicular to a direction in which the foreign matter storage portion extends is larger than a sectional area of the oil passage (36, 81) in a direction perpendicular to the direction in which the oil passage (36, 81) extends. a pump housing; an oil pump rotor housed in the pump housing and rotationally driven; an adjustment member (30, 130, 230) housed in the pump housing and that adjusts an amount of oil discharged from the oil pump rotor by being displaced under hydraulic pressure supplied to a hydraulic chamber between the pump housing and the oil pump rotor in a state where the oil pump rotor is rotatably held from an outer peripheral side; a seal member (41, 42) disposed in a portion where the adjustment member (30, 130, 230) and the pump housing face each other and that seals oil leakage to an outside of the hydraulic chamber; a seal member holding portion (34a, 35a, 134a, 234a) provided in the adjustment member (30, 130, 230) and that holds the seal member (41, 42); and an oil passage (36, 81) provided in the adjustment member (30, 130, 230) and through which the hydraulic pressure in the hydraulic chamber is drawn into the seal member holding portion (34a, 35a, 134a, 234a), wherein the seal member holding portion (34a, 35a, 134a, 234a) includes a foreign matter storage portion formed in a vicinity of the root of the seal member (41, 42) and that stores foreign matter contained in the oil drawn from the hydraulic chamber and that flows through the oil passage (36, 81), characterized in that the foreign matter storage portion is formed in the seal member holding portion (34a, 35a, 134a, 234a) so as to extend in a thickness direction of the seal member (41, 42) perpendicular to a direction in which the oil passage (36, 81) extends, and a sectional area of the foreign matter storage portion in a direction perpendicular to a direction in which the foreign matter storage portion extends is larger than a sectional area of the oil passage (36, 81) in a direction perpendicular to the direction in which the oil passage (36, 81) extends.