To smoothly and continuously drive a carriage to travel independently of the existence of a transfer region between carriage driving screw shafts.

The carriage 2 has two driven rollers 5, 6 fittable to the screw shafts 1A, 1C in one line and to the screw shafts 1B, etc. in the other line, respectively. The two screw shafts 1A, 1C and 1B, etc. and the two driven rollers 5, 6 are arranged so that, in another region than transfer regions B1, B2 between the two screw shafts 1A, 1B and between those 1B, 1C longitudinally adjacent to each other and different in line, the pair of driven rollers 5, 6 are alternately fitted to the screw shafts 1A, 1B, 1C in lines, and in the transfer regions B1, B2, before one driven roller 6 is moved apart from the upstream-side screw shafts 1A, 1B in one line, the other driven roller 5 is fitted to the downstream-side screw shafts 1B, 1C in the other line.