A power steering control device includes a torque sensor that detects a steering torque and outputs a torque signal having a torque neutral voltage is determined based on a predetermined reference voltage, a reference-voltage generator unit that generates the reference voltage, an A/D converter unit that A/D converts the torque signal and the reference voltage, a calculator unit that calculates a steering assist torque based on the A/D converted torque signal, a current controller unit that supplies a driving current in accordance with the assist torque to a steering assist motor, a reference-voltage generator unit that generates the reference voltage and outputs the reference voltage to the A/D converter unit and a fault diagnosis unit that monitors the A/D converted reference voltage and performs a predetermined fault diagnosis process.