Abstract: The inventive liquid separator of laboratory use can overcome the problems in the conventional separatory funnels used for liquid-liquid phase separation. The inventive apparatus comprises (a) a first bottle-like vessel with a mouth, (b) a second bottle-like vessel with a mouth connected with the first vessel at the mouths with air-tightness but disconnectable therefrom, (c) a porous membrane partitioning the first and the second vessels and made, preferably, of a sintered body of a water-repellent plastic resin such as a fluorocarbon polymer, and (d) an air-passage tubing opening at the ends in the first and the second vessels. When a two-phase mixture of an aqueous liquid and an organic liquid is taken in the first vessel positioned above the second vessel, the organic liquid can pass through the porous membrane to be transferred into the second vessel but the aqueous liquid is retained in the first vessel by virtue of the water-repellency of the fluorocarbon polymer.