A servo controller calculates an alternative movement amount, in a control cycle (n) in which a command cannot be received from the host controller, according to jerk calculated with reference to amounts of movement used for controlling the servomotor in former control cycles before the control cycle (n) and the movement amount used for controlling the servomotor in the previous control cycle before the control cycle (n). The servo controller controls movement of the servomotor by use of the alternative movement amount in the control cycle (n) in which the command cannot be received from the host controller.