Abstract: An absolute-type encoder is coupled to a drive shaft, which is rotatively driven by a motor, for detecting the amount of rotation of the drive shaft. The encoder includes a rotary disk storing position information and rotated in accordance with rotation of the drive shaft, a magnetic head for reading, in the form of a serial signal, the position information stored on the rotary disk, a counter for counting the holding information read by the magnetic head and outputting the information in the form of parallel information, and a battery for supplying operating power to the counter and magnetic head.