To make it possible to perform highly sensitive, highly accurate recording and to achieve the simplication of a recorder and the cost reduction by holding one end of a temperature/humidity detecting means on the side of a base stage, and bonding the other end to the driving shaft of a pen arm directly as a unitary body.

One end of a temperature detecting means 44 wound in a coil shape and one end of a humidity detecting means 57 bent and formed in a crescent shape are held in the grooves formed in respective rotors 33 and 47. At the same time, a tip part 46 of the other end (the same with the tip part of the detecting means 57) is inserted into a slit 43 (the same with the detecting means 57) of respective reference plates 42 and 56 attached to a supporting frame 32 and fixed. When the shapes of the detecting means 44 and 57 are changed in correspondence with the change in temperature/humidity, the rotors 33 and 47 are rotated in the foward direction and the reverse direction without through an expanding mechanism. Holding arms 36 and 50 and pen arms 40 and 54 forming a unitary body with the rotors are fluctuated. Pen tips 41 and 55 at the tip ends record the data of the chart paper on the side surface of a recording drum 31. Thus, the mechanism is simplified, the cost can be reduced, the sensitivity is improved and the highly accurate recording can be performed.