Abstract: A carriage position control circuit which locates a carriage at a center position of a printing sheet regardless of the paper size to maintain the printing sheet in contact with the platen. The carriage position control circuit includes a sensor (30) which moves, together with the carriage (2), in parallel to a center axis of the platen (1) of a serial printer and senses a printing sheet (10), a sheet position detector (43) which detects left and right edge positions of the printing sheet based on the sensor output and a center position calculating circuit (45) which calculates the center position of the printing sheet based on the left and right edge positions. The detection of the left and right edge positions and the calculation of the center position are performed before the leading edge of the printing sheet reach the anti-floating device (3).