To provide a motor controller for precisely detecting occurrence of a conduction failure in a power supply passage without detecting rotation angle speed based on a real rotation angle.

A conduction failure detection portion judges whether an induced voltage square sum Esq_αβ exceeds a prescribed threshold value E1 or not (step 602), and judges whether a motor rotation angle speed estimation value ωm_e is lower than a prescribed threshold value ω1 or not (step 603). When contradiction is detected that the motor rotation angle speed estimation value ωm_e is in a minimum region showing a non-rotating state (ωm_e<ω1, step 603:YES) although the induced voltage square sum Esq_αβ is in a maximum region corresponding to a maximum speed rotating state (Esq_αβ>E1, step 602:YES), it is judged that abnormality showing occurrence of the conduction failure exists in one of phases (step 604).