To protect the blades of an impeller and an inner peripheral surface of a housing from foreign matter sucked together with the contents in a pump comprising the impeller in the housing, by forming an oblique discharge guide groove communicated with an inner end of a discharge port over the whole width of the inner peripheral surface of the housing.

In a pump where an impeller 4 is mounted in a housing comprising an intake port 2 and a discharge port 3, and the impeller is rotated by a motor to obtain the pumping action, a compressive guide plate (a) is mounted on a compression zone 12 between the discharge port 3 and the intake port 2 on an inner peripheral surface 11 of the housing 1, whereby the compressing action comes into play. On this occasion, a discharge guide groove 6a is obliquely formed over the whole width W of the housing 1 at a position different from the compression zone 12 near an inner end 31 of the discharge port 3 in the housing 11. Whereby the foreign matter held and attached to the ends of the blades of the impeller 4 can be scraped off and the scraped foreign matter is discharged from the discharge port 3 together with the contents.