The present invention relates to a device for separating body fluid which can prevent contamination of the body fluid during centrifugation. The device for separating body fluid comprises: a first sealing cap having an elastic body in the center of a body； a first cylindrical housing which has one end portion screw-joined to the first sealing cap, and has an internal separation wall penetrated to have a first joining hole and arranged in the body； a cylindrical central housing which has one end portion screw-joined to the other end portion of the first cylindrical housing to enable screw-movement for each other, has a central separation wall penetrated to have at least one communication hole and arranged in the body, and is filled with body fluid； a second cylindrical housing which has one end portion screw-joined to the other end portion of the cylindrical central housing to enable screw-movement for each other, and has a second joining hole arranged in the body； a second sealing cap which is screw-joined to the other end portion of the second cylindrical housing； and a control unit having first and second stopper bars which are extended in a certain length in opposite directions toward the first joining hole and the second joining hole from the central separation wall and selectively closes or opens the first joining hole and the second joining hole upon reciprocal movement between the first and second cylindrical housings and the cylindrical central housing； selectively joining or closing a first space, formed between the first sealing cap and the first cylindrical housing, and the inner space of the central cylindrical housing to each other； and selectively joining or closing a second space, formed between the second sealing cap and the second cylindrical housing, and the inner space of the central cylindrical housing to each other.본 발명은 몸체 중앙에 탄성체를 갖는 제1밀봉캡 ； 상기 제1밀봉캡과 일단이 나사결합되고, 제1연결공을 관통형성한 내부격벽을 몸체 내부에 구비하는 제1원통하우징 ； 상기 제1원통하우징의 타단과 일단이 서로 나사이동이 가능하도록 나사결합되
