PURPOSE: To obtain a thermal transfer sheet having a wide range of excellent color reproducibility by laminating respective dye layers of three colors, that is, a yellow dye layer composed of a specific composition, a magenta dye layer and a cyan dye layer on one surface of a long base material sheet.

CONSTITUTION: A thermal transfer sheet for forming a color image is formed by successively laminating respective dye layers of three colors, that is, a yellow dye layer composed of a specific composition, a magenta dye layer and a cyan dye layer on one surface of a long base material sheet. As a yellow dye, there is a dye represented by formula I (R1 is an alkyl group or an aryl group and R2 is H or an alkyl group) and, as a magenta dye, there is a dye represented by formula II (R6 and R6 are an alkyl group or an aryl group, R8 is an aryl group or the like and R9 is an alkyl group or the like) and, as a cyan dye, there is a dye represented by formula III (R13, R14 and R16 are an alkyl group or the like, and R15 is H or an alkyl group).