Cut-off properties of porous membranes for microfiltration depend upon the pore-size distribution of those membranes, because the suspended particles are rejected by the porous membranes based on the size difference between the particle and the membrane pores. Therefore the control of pore size distribution during the membrane preparation is important to achieve a high reliability of the microfiltration processes. In this review, we summarized the conventional preparation methods of three kinds of porous membranes, that is, polymeric, ceramic and metallic membranes, and pointed out that the ceramic membrane has a bright prospect of developing the new industrial fields of microfiltration, although the efficient preparation method of this membrane to supply inexpensively has not been developed yet.