PURPOSE: To separate and remove oils effectively by a procedure in which a water- oil mixture is automatically sucked up from the upper layer of liquid level and then the sucked mixture is passed through a layer in which granular polypropylene of a specific molecular weight is floated.

CONSTITUTION: A water-oil mixture is sucked up from an intake whose sucking mouth can automatically follow the varying liquid level and can always suck up the surface layer of the liquid, and then passed through a polypropylene layer in which granular polypropylene of a molecular weight of 100,001W300,000 is floated in its framework, whereby particles of the oil are made coarser and then removed. For example, oily liquid is sucked up from the upper liquid layer by automatically following the then varying liquid level within the level difference H between the upper end of the outer cylinder 1 and the saw-teethed portion 5, and then sent into the coarsening cylinder 6 in which granular polypropylene is floated, where oils are coarsened, floated up to the upper side of the floating cylinder 7, and then removed from the pipe 8.