A thermal printer includes a platen roller, a thermal head, a frame including the thermal head and a side plate, the side plate including a platen roller receiving part configured to detachably support a bearing of the platen roller. The platen roller receiving part includes an open mouth for inserting and pulling out the bearing of the platen roller in a direction perpendicular to an axial direction of the platen roller, and the open mouth includes a protrusion formed on a downstream side in a rotation direction of the platen roller.