A switch apparatus for the horn device of a vehicle includes an inflator housing and a terminal unit provided in the inflator housing and configured to include a first contact element connected to the inflator and a second contact element connected to the inflator housing. A switching plate is installed using elastic members, which are spaced apart and insulated from the inflator housing, so that the switching plate makes contact with the inflator housing if the inflator housing is pressed, thereby operating the horn. A connector unit is coupled to the terminal unit with inflator wires and a horn wire, and is provided therein with a first connection element and a second connection element so that the horn wire and the inflator housing are electrically connected to each other.