A metal oxide which has a large pore volume, and is very useful as a catalyst support. An alkaline material is added to an aqueous solution in which a compound of a metal element for composing an oxide is dissolved, a resultant mixture is co-precipitated, an obtained precipitate is washed, a washed precipitate is stirred in water along with a surfactant, and is calcined. By adding the surfactant after washing, the pH is not changed so that the adding effect of the surfactant is achieved to its upper most limit, thereby obtaining a metal oxide which has a large pore volume and a large mean diameter of secondary particles, and exhibits excellent gas diffusion properties.