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.