A motor control device is configured in such a manner that a current detection circuit and an exciting circuit for a motor resolver share one grounding wire. A microcomputer that serves as a current detector sets a phase of an exciting current in such a manner that values of an excitation noise superimposed on an output voltage of the current detection circuit at respective timings (L1, H1, L2, H2, . . . ), at which the output voltage is acquired in one current detection process, are equal to each other. An electric power steering system is provided with the motor control device.