This application discloses a control device for controlling a motor configured to drive an oscillatory cyclo-speed reducer including an oscillatory gear portion formed with at least one hole at an eccentric position. The control device includes an angle acquirer for acquiring input information about an input rotational angle indicating a rotational angle of the motor, an estimator for estimating an angular error between the input rotational angle and an output rotational angle indicating a rotational angle of the oscillatory cyclo-speed reducer based on a quantity of the hole(s) and a corrector for determining a compensation current value in correspondence to the angular error and setting a magnitude of a current to be supplied to the motor by correcting a command current value using the compensation current value.