A method for producing a reaction product, with which the reaction product is obtained from a starting material through a particular organic synthesis reaction, the method includes (a) a step of setting a target wavelength to a peak wavelength of a reaction region involved in the organic synthesis reaction in an infrared absorption spectrum of the starting material; (b) a step of preparing an infrared heater that emits an infrared ray having a peak at the target wavelength from a structure constituted by a metal pattern, a dielectric layer, and a metal substrate stacked in this order from an outer side toward an inner side; and (c) a step of obtaining the reaction product by allowing the organic synthesis reaction to proceed while the infrared ray having a peak at the target wavelength is being applied to the starting material from the infrared heater.