In a method for producing a catalyst for oxidizing sulfurous acid gas which uses vanadium pentaoxide as a main catalyst, potassium salts as subsidiary catalysts and diatomaceous earth as a carrier; disclosed is a method for producing a parallel gas flow type catalyst for oxidizing sulfurous acid gas, characterized in that after an ingredient mixture of a solution containing vanadium pentaoxide and potassium salts, diatom earth, water and a binder containing sodium polyacrylate is knead, said ingredient mixture is extrusion molded into a shape in which gas passage holes have a honeycomb or grid structure.