Provided is an aldehyde production method that can provide target aldehydes with excellent aldehyde selectivity and a high conversion for a long period of time. The method includes bringing a mixed gas containing a vaporized primary alcohol and an inert gas into contact with a film-type dehydrogenation catalyst so as to dehydrogenate the primary alcohol in the mixed gas, thereby obtaining an aldehyde. The partial pressure of the primary alcohol in the mixed gas is 50 kPa or lower, and the film-type dehydrogenation catalyst is formed by providing a thin film catalyst layer on a support.