An electric motor control device comprising: a current control unit that has an electric current generator configured to generate a current command value to an electric motor based on at least a torque command value by referring to a table prepared in advance and that is configured to execute a current control mode in which a voltage command value applied to the electric motor is generated by the current control unit so that the current is controlled to match the current command value, which corresponds to the torque command value; a torque calculator configured to calculate a torque estimation value of the electric motor based on a torque computation formula; a voltage phase control unit configured to execute a voltage phase control mode in which a feedback operation is performed for a voltage phase based on a difference between the torque estimation value and the torque command value such that the torque estimation value matches the torque command value; and a control mode switching unit configured to switch to the voltage phase control mode in a high rotation area where a flux weakening control is performed, and to switch to the current control mode in another rotation area, characterized by a motor constant generator configured to generate a motor constant by using a temperature and a current detection value of the electric motor as parameters; wherein the torque calculator is configured to use the motor constant for calculating the torque estimation value, wherein the electric current generator is configured to generate the current command value under the same temperature environment as the temperature parameter of the motor constant used when the torque calculator calculates the torque estimation value. a current control unit that has an electric current generator configured to generate a current command value to an electric motor based on at least a torque command value by referring to a table prepared in advance and that is configured to execute a current control mode in which a voltage command value applied to the electric motor is generated by the current control unit so that the current is controlled to match the current command value, which corresponds to the torque command value; a torque calculator configured to calculate a torque estimation value of the electric motor based on a torque computation formula; a voltage phase control unit configured to execute a voltage phase control mode in which a feedback operation is performed for a voltage phase based on a difference between the torque estimation value and the torque command value such that the torque estimation value matches the torque command value; and a control mode switching unit configured to switch to the voltage phase control mode in a high rotation area where a flux weakening control is performed, and to switch to the current control mode in another rotation area, characterized by a motor constant generator configured to generate a motor constant by using a temperature and a current detection value of the electric motor as parameters; wherein the torque calculator is configured to use the motor constant for calculating the torque estimation value, wherein the electric current generator is configured to generate the current command value under the same temperature environment as the temperature parameter of the motor constant used when the torque calculator calculates the torque estimation value.