PURPOSE: To form a magnetic head rotating device where the degradation of the capacity is reduced when the number of magnetic heads is increased, by supplying selectively outputs from many magnetic heads arranged on a rotary cylinder to a rotor-side coil.

CONSTITUTION: A driving motor 39 is operated to rotate a rotary cylinder 34 in a constant speed, and the rotation angle of the rotary cylinder 34 is detected, and a control signal is impressed from a control signal generator 31 to a coil 30 in accordance with the rotation angle. Switches 26 and 27 are switched on a basis of this control signal, and the output of a magnetic head 25a is supplied to a coil 28a when the rotation angle of the rotary cylinder 34 is 0W90° or 270W360°, and the output of a magnetic head 25b is supplied to the coil 28a when the rotation angle of the rotary cylinder 34 is 90W270°. Similarly, the output of a magnetic head 25c is supplied to a coil 28b when the rotation angle of the rotary cylinder 34 is 0W90° or 270W360°, and the output of a magnetic head 25d is supplied to the coil 28b when the rotation angle of the rotary cylinder 34 is 90W270°. Outputs supplied to coils 28a and 28b of a rotor core 36 in this manner by switching are induced in coils 29a and 29b of a stator core 37 and are supplied to an external device.