A printing head adapted to be moved for scanning in a direction perpendicular to the direction of feed of a paper is provided with a sole printing element (printing hammer) adapted to be driven in an impacting manner by an electromagnetic driving device. A platen disposed to oppose to the printing head is provided with a plurality of projections formed on the outer peripheral surface thereof and extending substantially in parallel with the axis thereof. Each of the projections being adapted to oppose to the printing element in a crossing relation to the latter when it is brought to the position ahead of the printing element as a result of rotation of the platen. As the printing element collides with the projection while the platen is rotated, a dot is formed on the recording paper at the position of crossing between the printing element and the projection, so that various patterns such as letters, numerals, symbols, pictures and so forth are printed at a high speed by a sole printing element.