There is provided a thermal transfer sheet capable of being identified by a thermal transfer printing apparatus, as well as being capable of preventing color property changes in high-resolution printing and reducing production cost. The thermal transfer sheet (5) of an embodiment includes a dye layer (52) and a protective layer (54) on one surface of a substrate (50). The protective layer (54) contains an invisible light absorbing material and is provided with an identification mark (55) having at least one of a recessed portion and a protruding portion.