An objective is to detect a resolver malfunction without fail, using a low-cost resolver having the small number of the poles, and a control-motor system having advantage in small sizing and high-power outputting. In the control-motor system, the system for driving a 2m-pole motor based on a rotor rotation angle θ detected by a 2n-pole resolver, where m and n being counting numbers, is characterized in that: the sum of the square of a signal modulated by sin θ and the square of a signal modulated by cos θ in the resolver in which an excitation signal generated in said system is modulated by sin θ and cos θ in response to the rotor rotation angle θ of the resolver is compared to a predetermined malfunction threshold value, so that malfunction determination related to the resolver is performed, and also, given that the sum is a2 when the resolver is recognized to be in normal operation, the malfunction determination threshold value is made to be not smaller than {a×cos((π/2)/(m/n))}2.