An optical module control method is a method for controlling an optical module that includes a semiconductor light emitting element and an electronic cooling module configured to adjust a temperature of the semiconductor light emitting element. The optical module control method includes a step of detecting a temperature of a light emitting unit including the semiconductor light emitting element, and outputting temperature information of the semiconductor light emitting element; a step of detecting an environmental temperature and outputting temperature information of the environmental temperature, the environmental temperature being a temperature of environment where the light emitting unit is placed; and a step of controlling an output of the electronic cooling module on the basis of the temperature information of the semiconductor light emitting element and the temperature information of the environmental temperature, and adjusting the temperature of the light emitting unit.