Abstract: A polymer slurry formed by polymerizing ethylene or propylene optionally with other olefin monomer copolymerizable therewith in a hydrocarbon solvent such as propylene, propane, butane, etc., is continuously or intermittently supplied to a filter having a filtering surface on which a slight quantity of polymer particles are retained. Most of the hydrocarbon solvent is recovered by passing through the filtering surface, and the polymer particles are overflown from the filter to recover as a wet cake. By the use of such a specific filter, the quantity of the solvent to be vaporized can be greatly reduced.