A motor control device (4, 40) for driving a motor having an encoder that detects rotation of the motor, the motor control device (4, 40) comprising: a motor control unit that generates a command value to drive the motor according to a predetermined feedback scheme so that the rotation of the motor follows an operation command signal for driving the motor on the basis of the operation command signal and a feedback signal from the encoder that detects the rotation of the motor; a drive unit that supplies a drive current for driving the motor to the motor according to the command value from the motor control unit; an interrupt unit that interrupts transfer of a drive signal from the motor control unit to the drive unit according to the command value; and a safety control unit that executes an interrupting process of the drive signal via the interrupt unit when a determination is made that a failure has occurred in driving of the motor, wherein the safety control unit executes the interrupting process of the drive signal in the interrupt unit on the basis of a result of comparing a predetermined feedback value that is calculated with the feedback signal from the encoder with a state calculation value regarding a rotation state of the motor that is calculated according to a calculation model on the basis of the operation command signal and is comparable with the predetermined feedback value, wherein the safety control unit calculates an acceleration of the motor, and calculates the state calculation according to the acceleration of the motor; the motor control device (4, 40) being characterized in that: the encoder is configured to generate two independent feedback signals in response to the rotation of the motor, the safety control unit compares each of the two predetermined feedback values calculated from the two feedback signals with the state calculation value and compares the two predetermined feedback values to execute the interrupting process of the drive signal in the interrupting process, and the acceleration of the motor is calculated by dividing a load torque based on a torque command included in the operation command signal by a total inertia of the motor and load. a motor control unit that generates a command value to drive the motor according to a predetermined feedback scheme so that the rotation of the motor follows an operation command signal for driving the motor on the basis of the operation command signal and a feedback signal from the encoder that detects the rotation of the motor; a drive unit that supplies a drive current for driving the motor to the motor according to the command value from the motor control unit; an interrupt unit that interrupts transfer of a drive signal from the motor control unit to the drive unit according to the command value; and a safety control unit that executes an interrupting process of the drive signal via the interrupt unit when a determination is made that a failure has occurred in driving of the motor, wherein the safety control unit executes the interrupting process of the drive signal in the interrupt unit on the basis of a result of comparing a predetermined feedback value that is calculated with the feedback signal from the encoder with a state calculation value regarding a rotation state of the motor that is calculated according to a calculation model on the basis of the operation command signal and is comparable with the predetermined feedback value, wherein the safety control unit calculates an acceleration of the motor, and calculates the state calculation according to the acceleration of the motor; the motor control device (4, 40) being characterized in that: the encoder is configured to generate two independent feedback signals in response to the rotation of the motor, the safety control unit compares each of the two predetermined feedback values calculated from the two feedback signals with the state calculation value and compares the two predetermined feedback values to execute the interrupting process of the drive signal in the interrupting process, and the acceleration of the motor is calculated by dividing a load torque based on a torque command included in the operation command signal by a total inertia of the motor and load. the encoder is configured to generate two independent feedback signals in response to the rotation of the motor, the safety control unit compares each of the two predetermined feedback values calculated from the two feedback signals with the state calculation value and compares the two predetermined feedback values to execute the interrupting process of the drive signal in the interrupting process, and the acceleration of the motor is calculated by dividing a load torque based on a torque command included in the operation command signal by a total inertia of the motor and load.