A vehicle steering control device comprising: a first controller that controls a speed reduction mechanism in a steering mechanism in which a steering wheel and a rack-and-pinion that steers and drives a drive wheel are connected via a differential mechanism and the speed reduction mechanism is provided in a rack of the rack-and-pinion; and a second controller that controls the differential mechanism in the steering mechanism , wherein a first steering assist mode of assisting steering of a driver and a second steering assist mode of performing steering independently from the steering of the driver are provided as operation modes of the first controller and the second controller , a reference correlation defining a reference phase on a side of the steering wheel of the differential mechanism corresponding to a phase on a side of the rack-and-pinion of the differential mechanism , characterised by a correlation allowable region of the phase on the side of the steering wheel of the differential mechanism with respect to the reference phase are prescribed in the second controller , when the phase on the side of the steering wheel of the differential mechanism deviates from the correlation allowable region in the first steering assist mode, the second controller controls the differential mechanism at angular velocity in accordance with a control amount of the differential mechanism using the reference phase on the side of the steering wheel of the differential mechanism corresponding to the phase on the side of the rack-and-pinion of the differential mechanism as a target phase, and a phase angle until the phase on the side of the steering wheel of the differential mechanism reaches the target phase as a target angle. a first controller that controls a speed reduction mechanism in a steering mechanism in which a steering wheel and a rack-and-pinion that steers and drives a drive wheel are connected via a differential mechanism and the speed reduction mechanism is provided in a rack of the rack-and-pinion; and a second controller that controls the differential mechanism in the steering mechanism , wherein a first steering assist mode of assisting steering of a driver and a second steering assist mode of performing steering independently from the steering of the driver are provided as operation modes of the first controller and the second controller , a reference correlation defining a reference phase on a side of the steering wheel of the differential mechanism corresponding to a phase on a side of the rack-and-pinion of the differential mechanism , characterised by a correlation allowable region of the phase on the side of the steering wheel of the differential mechanism with respect to the reference phase are prescribed in the second controller , when the phase on the side of the steering wheel of the differential mechanism deviates from the correlation allowable region in the first steering assist mode, the second controller controls the differential mechanism at angular velocity in accordance with a control amount of the differential mechanism using the reference phase on the side of the steering wheel of the differential mechanism corresponding to the phase on the side of the rack-and-pinion of the differential mechanism as a target phase, and a phase angle until the phase on the side of the steering wheel of the differential mechanism reaches the target phase as a target angle. <EOS>