PURPOSE: To efficiently collect oil, by installing a rotor in water under the center of a double body and introducing the water and oil over the rotor by the rotation thereof and draining the separated water under the rotor.

CONSTITUTION: The rotor 3 is supported rotatably centering a rotary shaft 4 in the water under the center of the double body 1. The seawater containing the oil is introduced over the rotor by its rotation. The oil is separated from the water by their density difference in a separating portion 17. The separated oil is processed through a pump 10 and a suction port 7. The separated seawater is drained by the rotation of the rotor 3 from a hole 19 of the bottom of the body through the bottom of the separating portion 17. At that time, the water flow K is accelerated by a flap 16. The discharge of the separated water is promoted by the scoop effect of speed of the body.