Abstract: Improved apparatus for collecting effluent oil floating on a water surface. The improvements exist in that the apparatus utilizes a pair of side plates disposed in a forwardly opened arrangement, a weir which is inclined in a rear-downward direction with its opposite side edges contacted to the inner wall surfaces of the side plates under the water surface, and a slant plate which has its rear end positioned above the rear end of the weir in the rear of said side plates and has its opposite side edges fixedly secured to the inner wall surfaces of the side plates. Also, an oil leakage preventing plate is positioned midway between the rear end of the weir and the rear end of the slant plate and has its opposite side edges fixedly secured to the inner wall surfaces of the side plates to form a water discharge port between the oil leakage preventing plate and the rear end of the weir and to form an oily water intake port between the oil leakage preventing plate and the rear end of the slant plate.