In order to obtain an electromagnetic rotating machine of lightweight and high energy efficiency, which produces big torque for rotating a large-diameter fan, a coil A and coil B as excitation coils are disposed on an inner peripheral surface of a fan casing so as to face an outer circumference of the fan, and a coil M as an armature coil crosses at a central portion and is disposed on the outer circumference of the fan. The relationships |Iai|=|Iai+1| and Iai=−Iai+1, or |Ibi|=|Ibi+1| and Ibi=−Ibi+1 are obtained respectively for the coil A or coil B by a current control device (not shown). Moreover, the coil A and coil B are subjected to excitation control such that the direction of effective electromagnetic force, which is generated by an interaction between an effective magnetic field formed by the coil A and effective induced current applied to the coil M by the coil B, corresponds to the direction of rotation of the fan.