Abstract: A heating unit for heating a work piece 6 by heat conduction from a heat conducting plate 4 on which light from a light source 1 is irradiated, wherein the heat conducting plate 4 comprises a holding member 2 having optical transparency, and a heat conducting layer 3 which is provided on a surface of the holding member 2, and absorbs light emitted from a light source 1 and transmits the holding member 2, so as to generate heat. The heating unit has the heat conducting plate 4 in which deformation does not occur, and temperature thereof changes rapidly.