PURPOSE: To prevent breaking of paper, by controlling the rotary speed of a motor for driving a belt through a motor controller based upon a detection signal from a looseness detector thereby regulating and maintaining the loosening of a continuous paper within an allowable range.

CONSTITUTION: When a paper is being passed, a motor for driving a belt 4 is driven with a low speed and at this time a half-width continuous paper 5b is apt to loosen and when the looseness exceeds over a maximum allowable level, a looseness detector 2 is turned on to provide a detection signal to a controller 3 which switches the rotary speed of said motor 4 to a high speed so as to reduce the looseness of the half-width continuous paper 5b. When the looseness is reduced below a minimum allowable level, a looseness detector 1 is turned off and the controller 3 switches the motor 4 for driving a belt to a low speed so as to increase the looseness of the half-width continuous paper 5b. This function is repeated so as to regulate and maintain the looseness of the half-width continuous paper 5b within an allowable range.