To provide a thermal transfer printer which performs double-side printing while achieving a reduction in size and cost.

The paper transferring mechanism 5 includes a feed roller 511 rotating in forward and reverse directions and arranged between a paper feeding part 2 which holds a paper S wound in a roll shape and a common printing part 3 which performs thermal transfer printing to the front surface Sa and the rear surface Sb of the paper S, a first cutter part 53 which is arranged between the paper feeding part 2 and the feed roller 511 and cuts the paper S to a predetermined size, a paper turning part 54 with a turning route 54S where the paper S, subjected to thermal transfer printing to the front surface Sa by the printing part 3 and cut to the predetermined size by the first cutter part 53, can be turned upside down, and a paper delivery guide part 55 which guides the paper S, turned upside down by the paper turning part 54 and subjected to thermal transfer printing to the rear surface Sb by the printing part 3, to a delivery part 4.