To provide an ink ribbon winding mechanism that winds an ink ribbon along with movement of a carrier and can make a printing density constant and a printer having the mechanism.

This ink ribbon winding mechanism comprises a planetary gearing mechanism PG consisting of a sun gear 413 that rotates in forward and backward directions corresponding to the movement of the carrier 107, a holder 421 that is rotatably provided on the sun gear and has an urging section for urging the sun gear, a first planetary gear 451 that is provided on the holder and is engaged with the sun gear, and a second planetary gear 453 that is provided on the holder and is engaged with the sun gear, a winding means (a winding gear 461, an intermediate gear 463) that is engaged with either one of the first planetary gear and the second planetary gear in the planetary gearing mechanism PG and drives the ink ribbon in the winding direction, and a holder lock means HL for fixing the holder 421 at a neutral position where the first planetary gear and the second planetary gear are not engaged with the winding means.