A thermal printer includes a sprocket wheel (11) for forwarding sheets, a platen roller (9), a thermal head (26) pressed on the platen roller (9), and a reduction gear (8) by which a rotating drive of a motor is reduced and is communicated to the sprocket wheel (11) and the platen roller (9). The sprocket wheel (11) is engaged with perforations (33) of a transfer sheet (4), and the transfer sheet (4) and an ink ribbon (21) are forwarded while being tightly sandwiched between the platen roller (9) and the thermal head (26), and the ink of the ink ribbon (21) is thermally transferred onto the transfer sheet (4) by the thermal head (26). In the thermal printer, a gear (10) with a friction clutch is disposed between the platen roller (9) and the reduction gear (8), and the peripheral speed of the platen roller (9) is set to be higher than that of the sprocket wheel (11). A torque limitation value of the friction-clutch gear (10) is set equal to or less than a feeding load imposed between the transfer sheet (4) and the ink ribbon (21).