A robotic device having an arm including an actuator and inertial sensor, a first calculator adapted to calculate an angular velocity and an angular acceleration of the actuator based on a rotational angle data from an angle sensor, a second calculator adapted to calculate one of an angular velocity and an angular acceleration of the arm based on an output detected by the inertial sensor, and a comparator adapted to compare one of the angular velocity and the angular acceleration calculated by the first calculator and one of the angular velocity and the angular acceleration calculated by the second calculator with each other, and it is determined that the inertial sensor is at fault if an absolute value of the difference between the actuator and the arm in one of the angular velocity and the angular acceleration in the comparison section is larger than a threshold value.