A switch device includes a body with a switch member pivotably engaged with a top opening of the body and a first terminal and a second terminal respectively extend through two slots in a bottom of the body. A connection member is fixedly connected to an inside of the body and an adjusting member movably extends through a wall of the body and contacts the connection member. A U-shaped biasing member has a first end connected to the second end of a bi-metallic plate and a second end of the biasing member is connected to the connection member. The biasing member provides the bi-metallic plate proper flexibility so as to ensure the deformation of the bi-metallic plate to cut off the switch device when it is overloaded.