A control device includes at least a first task that has a first priority including processing execution performed by a program execution part and a command calculation part, a second task that has a second priority, lower than the first priority, including processing execution performed by a parsing part, and a third task that has a third priority including execution of a processing content different from the first task and the second task are set in a scheduler. The control device further includes a priority changing part monitoring a processing state of the parsing part, and when the processing state of the parsing part meets a predetermined condition, changing the second priority set to the second task corresponding to the condition.