To provide a manufacturing method is possible long-term stable operation while improving the unsaturated aldehyde and / or unsaturated carboxylic acids effective even at high-load reaction yield. Composite metal oxide catalyst multilayer packed stacked two or more layers of the catalyst layer in the tube axis direction at certain conditions including, and comprises a compound most gas outlet side catalyst layer is represented by a specific formula of tube axis containing catalyst, an unsaturated aldehyde and / or method for producing an unsaturated carboxylic acid.