1. An AC motor control system comprising: (a) velocity sensor means for sensing the velocity of an AC motor; (b) current sensor means for sensing an actual current flowing into said AC motor; (c) power drive circuit means for receiving a drive command and for driving said AC motor in accordance with said drive command; and (d) control means for performing a velocity loop computation at a first sampling period to obtain a current command from an offset velocity between a velocity command for said AC motor and said sensed actual velocity, and for performing a current loop computation to obtain an offset current between said current command and said sensed actual current, in said current loop computation, there is obtained a velocity compensation signal by amplifying said sensed actual velocity by a predetermined magnification, and the drive command for said power drive circuit is compensated by said velocity compensation signal, said current loop computation is executed at a second sampling period being shorter than said first sampling period, and, at the time of the velocity loop computation, the actual current at the relevant sampling instant is estimated from the current command value of the previous second sampling period, and the current command is computed from the estimated actual current and said offset current.