An image forming method using thermal transfer ink sheet containing a thermally diffusible dye and an image receiving sheet containing a metal ion containing compound capable of forming a metal chelate compound with the dye, comprising superimposing the ink sheet and the image receiving sheet and imagewise heating the ink sheet to transfer the dye to the image receiving sheet, wherein the imagewise heating is performed at a print rate of not more than 1.5 msec/line, and the image receiving layer further contains a metal ion species or at least one of a sorbitan fatty acid ester, a sorbitan fatty acid ester having a polyoxyethylene group, a phosphoric acid ester and compounds of the following formulas HO--[CH.sub.2CH.sub.2O].sub.n--[CH.sub.2CH(CH.sub.3)O].sub.m--H HO--(W--O).sub.p--H.