The present invention provides a protection device including a bimetal component and a PTC component. This protection device includes a resin base, a first terminal, a second terminal, a PTC component, a bimetal component, an arm, an upper plate and a resin cover. A portion of the first terminal configures a first electrode, and a portion of a second terminal configures the second electrode, and the first electrode and the second electrode are exposed outward at the bottom surface of the resin base. In a normal state, the first terminal, the arm and the second terminal are electrically connected in series. When the bimetal component is activated, the first terminal and the arm become electrically cut off while the first terminal, the PTC component, the bimetal component, the arm and the second terminal are electrically connected in series in the mentioned order.