PURPOSE: To control the speed of a printer rapidly and precisely by simple constitution by outputting a stop signal for a motor for control and forward turning and reversing and driving the motor when the speed of detection takes a fixed value to a set value.

CONSTITUTION: When the speed of printing is set by a speed setting section 1, the speed of printing is displayed by a display section 4 while being inputted to a control circuit 2. The control circuit 2 inputs a revolution-speed signal by a rotary plate 51 synchronizing with the revolution of a printing cylinder and a photocoupler 52. A relay 62 for driving is turned OFF and a motor 7 for controlling speed is stopped at a point of time when the speed of detection is lower than set speed only by a fixed number on the operation of speed increase. The motor 7 for controlling speed is stopped at a point on time when the speed of detection is higher than set speed only by a fixed number of the operation of speed decrease. The motor 7 for controlling speed is forward turned and reversed and driven by a relay 61 for contrarotation. Accordingly, the speed of a printer can be controlled rapidly and precisely.