PURPOSE: To transmit the revolving torque of a form carrying section accurately over a platen.

CONSTITUTION: A form conveyor has a driving gear 53 driven in the forward direction and the opposite direction and rotated together with a form carrying section, one-way clutch 45 transmitting only revolving torque in the forward direction, a platen gear 38 for transmitting revolving torque over a platen through a torque limiter and a changeover member 47 rotatably fitted to the shaft 46 of the form carrying section. The form conveyor is composed of a first planet gear 56 engaged with the driving gear 53 at all times, rotatably held by the changeover member 47 and transmitting revolving torque in the forward direction of the driving gear 53 to the platen gear 38 with a gear ratio slower than the peripheral velocity of the form carrying section, a second planet gear 57 engaged with the driving gear 53 at all times, rotatably held by the changeover member 47 and transmitting revolving torque in the opposite direction of the driving gear 53 to the platen gear 38 with a gear ratio faster than the peripheral velocity of the form carrying section, and a changeover driving section 58 reciprocating the changeover member 47.