PURPOSE: To obtain an easy-to-handle immersion heater which is directly immersed in a melted object in a die-cast furnace at hand and a crucible furnace or the like to enable a temperature to rise.

CONSTITUTION: A portable immersion heater comprising a handcart 1, control panel-provided control unit 2 provided on this handcart 1, preheating box 3 preheated by the control unit 2 provided on this handcart 1 and having an opening part 9 in the upper part and an immersed heater 4 inserted from the above-mentioned upper part opening 9 into this preheating box 3, preheated, lifted by a hoist type crane and directly immersed in a melted object in a die- cast furnace at hand or a crucible furnace.