PURPOSE: To reduce cost and to impart activity not inferior to that of an iron oxide/chromium oxide type pellet catalyst, by molding a mixture consisting of iron oxide, chromium oxide and a molding aid into a monolithic shape to form a carbon monoxide converting catalyst.

CONSTITUTION: Iron oxide and chromium oxide are used as effective catalytic components and one or more of an org. substance such as methyl cellulose, vinyl acetate, polyethylene oxide, polyacrylamide, polyvinyl alcohol or starch, one or more of an inorg. substance such as a glass fiber, a carbon fiber, a metal fiber or a kaoline fiber or a mixture of the aforementioned org. and inorg. substances is used as a molding aid at the time of the molding of a catalyst to be added to said catalytic components to perform mixing and kneading. Subsequently, the resulting mixture is molded into a monolithic shape to obtain a carbon monoxide converting catalyst.