Image forming method

An image forming method, comprising steps of:

• preparing a thermal transfer sheet comprising a dye layer formed on a substrate, the dye layer containing sublimable dye;
• preparing a decorative seal comprising a seal base material releasably provided on a release sheet, the seal base material having a layered structure comprising an adhesive layer and a film layered in this order from the release sheet side, the film containing a resin having a dyeing affinity to the sublimable dye contained in the dye layer, and the film having an elongation percentage in a range of not less than 150% and not more than 400% when determined by a test method in conformity with JIS-K-7127:1999;
• and
• thermally transferring the sublimable dye in the dye layer of the thermal transfer sheet onto the seal base material of the decorative seal by a sublimation type thermal transfer process, thereby forming a thermal transfer image on the seal base material.