A filter unit comprises a metallic supporting plate possessed of stepped through holes opening with a larger diameter in one main surface and with a smaller diameter in the other main surface (wherein the diameter ratio of larger-diameter openings to smaller-diameter openings is desired to be in the range of 1:0.01 to 1:0.5) or a pressureproof supporting plate having in one surface thereof inclined liquid flow grooves arranged in a radial pattern and concentric circular liquid flow grooves adapted to intersect the radially arranged liquid flow grooves and a membrane filter disposed on the surface of the supporting plate containing larger-diameter openings or liquid flow grooves. This filter unit is ideally used for finely dividing and uniformly sizing suspended lipid particles assuming a definite average particle size and a specific particle size distribution. The high-pressure sizing apparatus and the method for production of suspended lipid particles utilize the filter unit constructed as described above and rely essentially for their operation on effecting fine division of lipid particles in the suspension by supplying the suspension of lipid particles from the membrane filter side under pressure and causing the suspension to pass through the membrane filter. Thus, they constitute themselves effective measures for pharmacological products and cosmetic products which are in need of lipid particles assuming a definite average particle size and a specific particle size distribution.