PURPOSE: To enable a door to bear frequent openings and closings by making the hardness of the projection that is fixed to the main body of a heating device and the hardness of the projection of a mounting device that is fixed to a door higher than the hardness of the mounting devices.

CONSTITUTION: The projection 4b of a first mounting device 4 that is fixed to the main body of a heater and the projection 5b of a second mounting device 5 that is fixed to a door 2 have a hardness higher than the hardness of the first and second mounting devices 4 and 5. With this arrangement the wear in the projections 4b and 5b which occurs by frequent openings and closings of the door 2 becomes less so that it is possible to provide a door stopping means with a high reliability which is one of the safety functions.