A motor-driven power steering apparatus is provided with a sub control system including a map memory means storing a first window time setting map M1 and a second window time setting map M2 in which a window time is set shorter, a window time setting map selecting means selecting the first window time setting map M1 at a time when a torque change amount dT and a current change amount dIm are both smaller than respective predetermined change amounts, and selecting the second window time setting map M2 in the other cases, a window time deciding means collating a point coordinate of a combination of a steering torque and a motor current with the selected window time setting map so as to decide a window time, and a motor drive stop determining means determining the motor drive stop in the case that the point coordinate exists in a region corresponding to the decided window time for the window time, and when a motor drive stop determining means determines the motor drive stop, the drive of the motor controlled so as to be driven by a main control system is stopped.
