The utility model provides a wire fixing device. The wire fixing device comprises an end cover, a maintenance cover and a fixing device; the outer side of the end cover is provided with a wire groove; the inner side of the maintenance cover is provided with a pressing device; and after the maintenance cover and the end cover are fixed by the fixing device, the pressing device is pressed on the wire groove, and seals and blocks the groove top of the wire groove. According to the wire fixing device of the utility model, the outer side of the end cover is provided with the wire groove; after entering a water heater from exterior of the water heater through a wire entering hole in the end cover, a power source wire is installed in the wire groove, and the end cover is covered with the maintenance cover; and after the maintenance cover and the end cover are fixed by the fixing device, the pressing device arranged at the inner side of the maintenance cover is pressed on the wire groove and is matched with the top end of the groove wall of the wire groove, so that the groove top of the wire groove which was in an open state originally can be sealed and blocked, and the power source wire is pressed and fixed, and therefore, the power source wire can be prevented from escaping from the wire groove; the pressing device and the maintenance cover are integrated together so as to form one body; the maintenance cover and the end cover can be fixed together with one screw which is adopted as the fixing device, so that the number of screws and installation positions can be saved, and production cost can be saved.