PURPOSE: To arrange the pens in the recorder so that they can be exchanged by providing a unitary body wherein the pens having the same shape and their associated mechanism are incorporated.

CONSTITUTION: Pen driving and operating assemblies D1, D2, and D3 hold the tips of pairs of pens 11a and 11b, 11c and 11d, and 11e and 11f, so that the tips are contacted with a curved recording surface 6 and directed toward a drum shaft 7 which is the center of the curvature, (i.e. along the lines of radiuses). The contact points are sequentially shifted in the direction of the curvature. The pens 11a, 11b...11f are directly supported by corresponding pen carriages 12a, 12b...12f. Said pen carriages are slidably supported by corresponding guide shafts 14, which are bridged on side plates 13 of the assemblies D1, D2, and D3. Main parts of the pen driving mechanisms which will be described later and vertical pen driving mechanisms are arranged in the inside of the plates 13. At the rear ends of the side plates 13, motor casings 15 are supported.