To provide a printer for a tag by which a pitch size can be easily corrected even though the tag 20 for installing a printer slips in a conveying path and the correction is flexible.

The thread threading hole 21 has side end portions 21A, 21D formed long in a straight line shape in a direction perpendicular to the conveying direction of the tag 20 in the conveying path, the center portion of the perforation 22 for cutting and separating extending in a direction perpendicular to the conveying direction is formed in an elongate rectangular hole 23 extending in a width direction of the tag 20 in the tag 20, and a transmission type sensor for detecting positions of the side end portions 21A, 21D of the thread threading hole 21 and either one of the side end portions 23A, 23D of the rectangular hole 23 is installed, paying attention to that a second portion to be detected is constituted by forming the center portion of a perforation 22 for cutting and separating formed separately from the thread threading hole 21 as a first portion to be detected into an elongate rectangular hole 23.