Three kinds of inorganic dynamic membranes for ultrafiltration were formed on ceramic support tubes by filtering colloid solutions of Zr(IV), Al(III) and Fe(III). Permeate fluxes and molecular weight cut-off values were controlled not only by conditions such as pressure, pH and colloid concentration during membrane formation, but also by the membrane formation time. The Zr(IV) dynamic membrane had the best mechanical stability among the three kinds of membranes obtained in this study. This membrane also had good resistance to temperature up to 353 K and to pH in the range of 3-11. Results of analysis based on the steric-hindrance pore model suggested that the active layer thickness of Zr(IV) membranes, namely the thickness of the deposit layer, was smaller than that of a polymer ultrafiltration membrane, a membrane that had almost the same rejection ability as the Zr(IV) membrane.