PURPOSE: To enhance printing property, white color effect or the like, by a method wherein a mixture of a colorless color forming lactone dye, a phenol compound, silicic acid having an average particle diameter of not larger than 2μ and a BET specific surface area of not larger than 120m2/g and an adhesive is applied to a paper.

CONSTITUTION: A colorless color forming lactone dye, a phenol compound capable of developing the color of the dye when being heated, a pigment consisting mainly of particulate silicic acid having an averge particle diameter of not larger than 2μ and a BET specific surface area of not larger than 120m2/g and an adhesive are mixed with each other by adding a dispersing liquid to prepare a coating liquid for producing a heat-sensitive paper. The coating liquid is applied to a paper by an ordinary means such as an air knife coater, a blade coater or a roll coater, is dried, and is calendered to obtain a high-sensitivity heat- sensitive paper. The color forming lactone dye may be crystal violet lactone or the like, while the phenol compound may be 4,4'-isopropylidenediphenol or the like.