PURPOSE: To catch and separate oil, etc. contained in waste gas surely, by arranging impellers for collecting oil by sticking and baffle plates for collecting the oil by collision organically in an exhaust duct so that its oil collecting efficiency is maximum.

CONSTITUTION: When a waste gas containing oil mist passes through a grease filter 2 and a device in sequence by the suction of an exhaust fan 8, massive oil particles in the waste gas firstly caught by the grease filter 2 and are gathered in an oil receiver 4. The oil included in the waste gas which has passed through the filter 2 is firstly caught by sticking by the vanes of an impeller 11 and is made to stick to the inner surface of an attached duct 9 by a centrifugal force, and simultaneously, the oil is caught by collision by a baffle plate 14 at the 1st stage, and both of the caught oil fall down along the inner surface of the duct 9 to an oil receiver 17. The remaining oil in the gas is caught by sticking by the vanes of an impeller 12 at the 2nd stage, and is made to stick to the inner surface of the duct 9 by a centrifugal force, and simultaneously the oil is caught by collision by a baffle plate 14 of the 2nd stage, and both of the caught oil fall down along the inner surface of the duct 9 to an oil receiver 17 through an oil discharging port 16.