An air bag door fastening structure having an air bag door including a base layer of synthetic resin, coupled at one side end thereof through hinges with an instrument panel and at the other side end thereof through breakaway members with the instrument panel characterized in that each breakaway member comprises two fastening portions integrally coupled through a thin integral hinge with each other as a coupler in such a manner that one fastening portion is coupled fixedly with the base layer or integrated with the base layer and the other fastening portion is coupled fixedly with the instrument panel.
