PURPOSE: To obtain an image having good gloss with smaller electric power by using a thermal head having heating elements to constitute a heat fixing device constituting an image recorder.

CONSTITUTION: An original is placed on an original platen 6 and light from a light source 7 is projected to expose microcapsule paper 4 went from a conveyor 3. The exposed capsule paper 4 and a color developer medium 9 are superposed on each other and are passed through a pressure developing device 8 consisting of a pair of press rollers 8a and 8b, thereby crushing capsules of the paper 4 to generate the image on the medium 9. The gloss is thereafter generated on the surface of the medium 9 by using the heat fixing device 11. The device 11 is constituted in the following manner at this time. The device 11 is constituted of the thermal head unit 2 having the many very small heating elements and a contact sensor part 21 consisting of an optical lens and photodetecting element is provided before this unit. The data obtd. therein is inputted to a central processing unit 22. The gloss is thus generated in the image part by selecting the heating elements in the unit 2 and the character part is held intact.