A drive control apparatus for driving an AC motor by applying a rectangular wave voltage thereto, comprising: a torque estimating unit that is configured to obtain an estimated torque of a rotor of the AC motor; a torque deviation detecting unit that is configured to detect a torque deviation as a difference between the estimated torque and a torque command value representing a required torque of the AC motor; and a rectangular wave voltage controller ( 56, 60) that is configured to control a state of the rectangular wave voltage applied to the AC motor, through torque feedback control based on the torque deviation, so that a torque of the rotor approaches the torque command value, wherein the rectangular wave voltage controller ( 56, 60) comprises: a rotation speed detector that is configured to detect a current rotation speed of the AC motor; characterized in that the rectangular wave voltage controller ( 56, 60) further comprises: a rectangular wave voltage phase switching unit that is configured to switch, in a predetermined order, a plurality of predetermined rectangular wave voltage states corresponding to different phase values of the rectangular wave voltage; and a switching timing controller that is configured to set a switching timing of the rectangular wave voltage states to a timing that deviates from a reference timing determined based on the current rotation speed, by a length of time corresponding to the torque deviation. a torque estimating unit that is configured to obtain an estimated torque of a rotor of the AC motor; a torque deviation detecting unit that is configured to detect a torque deviation as a difference between the estimated torque and a torque command value representing a required torque of the AC motor; and a rectangular wave voltage controller ( 56, 60) that is configured to control a state of the rectangular wave voltage applied to the AC motor, through torque feedback control based on the torque deviation, so that a torque of the rotor approaches the torque command value, wherein the rectangular wave voltage controller ( 56, 60) comprises: a rotation speed detector that is configured to detect a current rotation speed of the AC motor; a rotation speed detector that is configured to detect a current rotation speed of the AC motor; characterized in that the rectangular wave voltage controller ( 56, 60) further comprises: a rectangular wave voltage phase switching unit that is configured to switch, in a predetermined order, a plurality of predetermined rectangular wave voltage states corresponding to different phase values of the rectangular wave voltage; and a switching timing controller that is configured to set a switching timing of the rectangular wave voltage states to a timing that deviates from a reference timing determined based on the current rotation speed, by a length of time corresponding to the torque deviation. a rectangular wave voltage phase switching unit that is configured to switch, in a predetermined order, a plurality of predetermined rectangular wave voltage states corresponding to different phase values of the rectangular wave voltage; and a switching timing controller that is configured to set a switching timing of the rectangular wave voltage states to a timing that deviates from a reference timing determined based on the current rotation speed, by a length of time corresponding to the torque deviation.