An optical module includes a package, which accommodates an optical system. A package main body has an opening. A lid is attached to the main body to close the opening of the main body. The lid seals the package. An anti-deterioration agent for preventing deterioration of the optical system is located inside the package at a position out of a light path of the optical system. The anti-deterioration agent includes at least one of desiccant and deoxidant.