A control device comprising: a power converter configured to convert electric power of a power supply into electric power for driving an AC electric motor having saliency; a current detector; an estimation module configured to repeatedly calculate an angle estimation value correlated with a magnetic pole position of the AC electric motor; and a storage module configured to store the angle estimation value, wherein the estimation module includes a response information calculation module configured to calculate response information indicating a change in an output current detected by the current detector, the output current being associated with the AC electric motor, wherein the change in the output current results from a change in an output voltage, and an angle calculation module configured to calculate the angle estimation value based on the response information and the angle estimation value of a past which is stored in the storage module to compensate for an angle estimation error resulting from an electromagnetic mutual interference between coordinate axes associated with an orthogonal coordinate of the AC electric motor, characterised in that the control device further comprises a coefficient calculation module configured to calculate an interference coefficient correlated with the electromagnetic mutual interference based on the angle estimation value of the past which is stored in the storage module, and the response information, and wherein the angle calculation module is further configured to calculate the angle estimation value based on the response information and the interference coefficient, wherein the control device further comprises a component calculation module configured to calculate, based on the response information, a sine component of the angle estimation value of a case where the mutual interference is ignored and a cosine component of the angle estimation value of a case where the mutual interference is ignored, wherein the angle calculation module calculates the angle estimation value by using the sine component, the cosine component, and the interference coefficient. a power converter configured to convert electric power of a power supply into electric power for driving an AC electric motor having saliency; a current detector; an estimation module configured to repeatedly calculate an angle estimation value correlated with a magnetic pole position of the AC electric motor; and a storage module configured to store the angle estimation value, wherein the estimation module includes a response information calculation module configured to calculate response information indicating a change in an output current detected by the current detector, the output current being associated with the AC electric motor, wherein the change in the output current results from a change in an output voltage, and an angle calculation module configured to calculate the angle estimation value based on the response information and the angle estimation value of a past which is stored in the storage module to compensate for an angle estimation error resulting from an electromagnetic mutual interference between coordinate axes associated with an orthogonal coordinate of the AC electric motor, characterised in that the control device further comprises a coefficient calculation module configured to calculate an interference coefficient correlated with the electromagnetic mutual interference based on the angle estimation value of the past which is stored in the storage module, and the response information, and wherein the angle calculation module is further configured to calculate the angle estimation value based on the response information and the interference coefficient, wherein the control device further comprises a component calculation module configured to calculate, based on the response information, a sine component of the angle estimation value of a case where the mutual interference is ignored and a cosine component of the angle estimation value of a case where the mutual interference is ignored, wherein the angle calculation module calculates the angle estimation value by using the sine component, the cosine component, and the interference coefficient.