The invention provides a heat-sensitive recording material, which is highly sensitive, is almost free of staining on the background, and gives a recorded image excellent in stability during storage, by using a finely divided sensitizer dispersion excellent in shelf stability produced in a short time with high volumetric efficiency. The invention relates to a method of producing a sensitizer dispersion, which comprises emulsifying and finely dividing a heat-sensitive recording sensitizer by melting under heating in an aqueous emulsifying dispersant, and then crystallizing the finely divided emulsified dispersion under rapid cooling, wherein the sensitizer is at least one member selected from the group consisting of 1,2-bis(phenoxy)ethane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, p-benzylbiphenyl, di-p-methylbenzyl oxalate, and β-naphthyl benzyl ether.