  Yokoyama's gaugeon formalism is knwon to admit $q$-number gauge
transformation. We introduce BRST symmetries into the formalism for the
Yang-Mills gauge field. Owing to the BRST symmetry, Yokoyama's physical
subsidiary conditions are replaced by a single condition of the Kugo-Ojima
type. Our physical subsidiary condition is invariant under the $q$-number gauge
transformation. Thus, our physical subspace is gauge invariant.
