A coating process includes adding a body to a reactor; adding a metal alkoxide or precursors thereof to the reactor; adding a catalyst for the hydrolysis of the metal alkoxide to the reactor; and coating the surface of the body with a metal oxide-containing coating layer through the hydrolysis and dehydration condensation of the metal alkoxide. The addition of a body precedes at least one of the addition of a metal alkoxide or precursors thereof and the addition of a catalyst.