Method for producing reaction product

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 comprising:

• (a) a step of setting a target wavelength to a peak wavelength of a reaction region in intramolecular reactions, intermolecular reactions between identical molecules, or intermolecular reactions between dissimilar molecules 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, which has a full width at half maximum of 1.0 μm or less 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, which has a full width at half maximum of 1.0 μm or less at the target wavelength, is being applied to the reaction region in intramolecular reactions, intermolecular reactions between identical molecules, or intermolecular reactions between dissimilar molecules of the starting material from the infrared heater.