Galtier's men progressed to the group stage on penalties following a 1-1 aggregate draw against Turkish outfit Karabukspor on Thursday.
And 48-year-old Galtier compared his team's achievement to winning silverware or reaching the UEFA Champions League.
"We did not win a trophy, we are not qualified for the Champions League but for us in Saint-Etienne, it's a big step," he is quoted as saying by L'Equipe.
"I hope we will use the experience of the group matches as a chance to improve.
"It's a great feeling.
"On a personal level, elimination would have been difficult to digest, even though in this game I could not fault the players."
Saint-Etienne will discover their group-stage opponents when the draw is made on Friday.