PURPOSE: To prevent the increase in thickness of recording paper beyond the required value by providing a control means for adjusting the fusing amount of a thermal recording means, which diffuses an acceptance layer in response to the roughness, the base color and the like of the surface of the paper used, and variably adjusting the thickness of the acceptance layer appropriately in response to the supplied recording paper.

CONSTITUTION: An image forming apparatus forms an acceptance layer with a pretreating material on the surface of recording paper from a paper feeding mechanism by thermal transfer. Characters, graphics and the like are printed on the acceptance layer by the thermal transfer. A thermal transfer ribbon is formed by applying the pretreating material along the transfer direction, and then forming four frames of dyes, which are applied in the sequence of, e.g. yellow, Magenta and cyan as one set. Many sets of the ribbons are continuously provided. An adjusting switch W, which is the control means for adjusting the fusing amount, in a thermal recording means 20, fuses the acceptance material in response to the roughness, the base color and the like of the surface of the recording paper used. A potential U of a power supply terminal V0 is adjusted only in printing. The appropriate thickness of the layer suitable for the recording paper is adjusted by forming several samples beforehand, or adjusted by trial printing at every printing.