The present invention aims to provide a steam treatment process for stably preparing steam-treated roasted coffee beans having constant flavor quality by reducing variation in the degree of roasting between different sites in the system during steam treatment of roasted coffee beans without complicating operation processes or increasing costs.Steam at a temperature lower than the temperature necessary to advance the degree of roasting of coffee beans is supplied to an apparatus in which the roasted coffee beans are placed until condensed liquid produced in the apparatus has been discharged from the apparatus, and then, the temperature of steam supplied into the apparatus is raised until a temperature becomes sufficient for advancing the degree of roasting of coffee beans.
