Abstract: A dual-use electric plug including a base having vertical receiving chamber and a horizontal side hole, two blades fixedly and perpendicularly fastened to the front side of base for connection to the black wire and the white wire, a grounding prong supported on a spring inside the vertical receiving chamber and moved between the working position outside the vertical receiving chamber for connection to the grounding wire, and the non-working position inside the vertical receiving chamber, and a spring-supported press bar to hold the grounding prong in the working position, wherein the grounding prong can be moved back inside the vertical receiving chamber and retained in the non-working position by depressing the press bar and then releasing it.