To provide a UV irradiation type membrane filtration apparatus which enables effectively suppressing the clogging of a filtration membrane without exerting influence on the filtration membrane.

This membrane filtration apparatus uses an immersion type filtration membrane of external pressure suction type in which the filtration membrane is immersed in a filtration treating tank and the filtration treatment of the raw water is performed. Therein, a UV irradiation part which performs bactericidal treatment of the raw water is further disposed in the filtration treating tank.