The utility model discloses a thermal printer which comprises a glue roller, a main bracket, a locating rotating shaft, a movable frame, a bracing plate, a positioning slot, a printing head, a first elastic element and a locking mechanism, wherein, the glue roller is supported by the main bracket; the locating rotating shaft is positioned on one side of the main bracket apart from the glue roller; the movable frame is articulated with the main bracket through the locating rotating shaft and can be opened or closed relative to the main bracket; the bracing plate is positioned in the movable frame and can move up and down relative to the movable frame; the positioning slot is formed on the bracing plate and jointed with the locating rotating shaft; the printing head is positioned on the bracing plate and corresponds to the glue roller; the first elastic element is positioned between the movable frame and the bracing plate; and the locking mechanism can lock the main bracket and the movable frame. When a printing head subassembly is switched to open or close, the positioning slot of the thermal printer does not need to separate from or buckle with the locating rotating shaft, so that the abrasion caused by repeated separation and buckling between the positioning slot and a locating shaft in the prior art can be avoided, the reliability of a locating mechanism can be improved, and the service life can be prolonged.