VANE PUMP

An oil supply groove 12 in communication with a pump room 2A is formed above a bearing 2B of a housing 2, and an open air groove 14 in communication with an atmospheric air is formed at a position rotated around the bearing 2B by 90° from the oil supply groove. In a shank 3B of a rotor 3, a branch passage 11a branching from an oil passage 11 formed in its axial direction to the diametrical direction of the shank, and an open air passage 13 formed in the direction perpendicular to the branch passage are formed. Then, the branch passage and the oil supply groove communicate with each other, at the same time, the open air passage and the open air groove are arranged to also communicate with each other, and when the oil passage and the oil supply groove communicate with each other as the rotor stops, then an atmospheric air flowing in from the open air passage eliminates a negative pressure in the pump room, thereby the lubricating oil is prevented from flowing into the pump room in large quantities. An amount of the lubricating oil flowing into pump room at stop of the rotor can be reduced to prevent the vane from being damaged and an amount of the lubricating oil consumed due to rotation of the rotor can be controlled.