PURPOSE: To heat an objective only by one touch operation, by providing a rotationable lid to close the opening of a heat-generation chamber and a cutter on the lid to cut a water container.

CONSTITUTION: A heat-generation vessel 5 is fitted by winding caulk 7a to a container body 1 at the periphery of the flange 7. The cylindrical part 6 forms a heating chamber 9 having an opening 8 at the one end thereof, extrud ing in the container body 1. A lid 20 of the opening 8 is fitted rotationally, fitting a ring-form periphery 21 at the winding caulk 7a, to rotate together with a cutter 30 equipped in the lid 20. A water container 10 having a flange 11 and a sheet of sealed lid 13 is inserted up-side-down into the heating chamber 9. The flange 11 is fitted into a ring-form ditch 6a of the cylindrical part 6. The sheet of sealed lid 13 contacting the sealed face 14 is cut to be an arch shape 14c by a tip 33 of the cutter 30 only by turning the lid 20 because the sealed face 14 of the water container 10 is formed to be a taper. Objectives to be heated 2 are heated by the reaction heat with a heating reagent 15 in the heating chamber 9 due to flow-in water.