A heat-recording material comprising a microencapsulated diazonium salt and a coupler was studied. In this case, the capsule contained a specific diazonium salt and no core oil. An oilless microcapsule showed good heat-recording characteristics by stabilizing the solution state of a diazocontaining organic phase, and by using a capsule-wall former which reacts with H2O quickly and creates a capsule with high Tg. The structure of the microcapsule was not the ordinary core/shell but a sphere, wherein the diazonium salt existed almost uniformly.