In a controller, a first switch unit establishes electrical connection between a power-off brake and a power source when a servomotor is energized. The electrical connection causes the power-off brake to be released. A second switch unit is provided between the power-off brake and the power source. The second switch unit establishes electrical connection between the power-off brake and the power source upon being manually operated during the servomotor being deenergized. A calculating unit calculates a driving speed of the joint by the servomotor. A determining unit determines whether the calculated driving speed of the joint is greater than a predetermined threshold speed. An interrupting unit interrupts a supply of electrical power from the power source to the power-off brake through the electrical connection established by the second switch unit when it is determined that the calculated driving speed of the joint is greater than the predetermined threshold speed.