Abstract: In an electrically driven power steering system and a control apparatus for the electrically driven power steering system which are capable of reducing a development of a noisy sound due to a magneto-strictive sound. A voltage V(Thys) corresponding to each of PWM pulses achieving time Thys (a third predetermined value) corresponding to a hysteresis is added to one of the voltage command values of a voltage large phase from among three phase first voltage command values (Vu1*, Vv1*, Vw1*) and this voltage V(Thys) is subtracted from one of the remaining voltage command values which is a voltage small phase to derive virtual voltage command values, and the virtual voltage command values (Vu*im, Vv*im, Vw*im) are mutually compared to carry out a voltage magnitude (large, middle, small) phase determination.