A controller of an electric motor for improving operation efficiency in performing electric conducting control of the electric motor of an axial air-gap type is provided. Therefore, the controller of the electric motor (3) of the axial air-gap type including a rotor (11) having a permanent magnet, a first stator (12a) and a second stator (12b) oppositely arranged through the rotor (11) in a rotation axis direction of the rotor (11), and armature windings (13a, 13b) mounted to the first stator (12a) and the second stator (12b) has an electric current command determining section (30) for switching between a both-side stator driving mode for conducting a driving electric current to both the armature winding (13a) of the first stator (12a) and the armature winding (13b) of the second stator (12b), and a one-side stator driving mode for conducting the driving electric current to only the armature winding (13a) of the first stator (12a) in accordance with a request value Tr_c of output torque of the electric motor (3).