An electric power steering device, comprising: an electric motor that causes a vehicle steering device to rotate; and a control unit that controls the electric motor, the electric motor having a stator including at least two independent sets of coil winding groups, the control unit having a control portion, having a CPU as a core, that computes and outputs a control amount, and a drive circuit that independently drives each winding group of the electric motor, wherein the control portion has a failure determination function portion that can detect a failure of each of a plurality of regions of the electric power steering device such as inverter circuits, noise filters, input circuits or the like, said regions being divided into sets corresponding to the sets of coil winding groups, the control portion further including a memory that stores a region in which the failure has occurred and details of the failure for each detected failure, and stores the failure details categorized into at least two kinds of failure mode, and the control portion is configured in such a way that, when detecting a first failure, continues control in a normal set in which no failure has been detected, or continues control by combining a portion, i.e. region or regions in which no failure has occurred of a set in which the failure has occurred and the normal set, and when detecting a second or subsequent failure, determines a continuation of control also considering a past failure mode and region in which a failure has occurred, and when continuing control, selects a set in which control can be carried out, or continues control by employing one portion, i.e. region or regions of each set in which no failure has occurred. an electric motor that causes a vehicle steering device to rotate; and a control unit that controls the electric motor, the electric motor having a stator including at least two independent sets of coil winding groups, the control unit having a control portion, having a CPU as a core, that computes and outputs a control amount, and a drive circuit that independently drives each winding group of the electric motor, wherein the control portion has a failure determination function portion that can detect a failure of each of a plurality of regions of the electric power steering device such as inverter circuits, noise filters, input circuits or the like, said regions being divided into sets corresponding to the sets of coil winding groups, the control portion further including a memory that stores a region in which the failure has occurred and details of the failure for each detected failure, and stores the failure details categorized into at least two kinds of failure mode, and the control portion is configured in such a way that, when detecting a first failure, continues control in a normal set in which no failure has been detected, or continues control by combining a portion, i.e. region or regions in which no failure has occurred of a set in which the failure has occurred and the normal set, and when detecting a second or subsequent failure, determines a continuation of control also considering a past failure mode and region in which a failure has occurred, and when continuing control, selects a set in which control can be carried out, or continues control by employing one portion, i.e. region or regions of each set in which no failure has occurred.