Abstract: A tape printer that includes: a cartridge loading portion to which a tape cartridge is loaded, the tape cartridge including a cartridge case and a platen roller accommodated in the cartridge case, the cartridge case having a positioning recess and a first detection target portion of which shape is varied depending on various types of tape cartridge; a platen shaft provided in the cartridge loading portion and inserted into the platen roller; a first detection unit provided in the cartridge loading portion, of which output changes depending on the shape of the first detection target portion; and a positioning projection provided at a position farther than the first detection unit with respect to the platen shaft in the cartridge loading portion when seen from a near side in a loading direction of the tape cartridge, and engaging with the positioning recess.