In a wire-dot impact type printer a cylindrical platen and a printing paper are rotated or transported at the same rate, by connecting them to a single and common electric motor through a first and second transmission mechanisms, respectively. The first transmission mechanism directly connects the platen to the motor to cause the former to rotate together with rotation of the latter in any direction, whereas the second transmission mechanism includes a clutch composed of a first and a second members rotatable about a common center axis but separately from each other in which the first member is caused to rotate together with rotation of the motor in any direction while the second member is caused to rotate together with the first member being rotated in one direction but prevented from rotating when the first member is rotated in the other direction. In the latter case the platen is rotated for color changing operation, but the printing paper is prevented from running through the printer.