PLC device that transmits an instruction to a control device

A PLC device comprising:

• a ladder control unit that interprets a ladder program and controls an input/output signal in accordance with the interpretation;
• a special instruction control unit that sets, on the basis of an instruction from the ladder control unit, a priority degree indicating a degree of priority for executing predetermined processing to a special instruction for performing the predetermined processing in a control device that controls an industrial machine, the priority degree being set as an argument in the special instruction, and transmits the special instruction in which the priority degree is set to the control device, the control device being a computerized numerical control (CNC) device different from the PLC device;
• an instruction storage determining unit that determines whether or not to queue the special instruction according to an operation state of the control device, the operation state indicating that communication with the control device is not possible due to the control device being unable to respond;
• and
• an instruction storage unit that sequentially stores the special instruction transmitted by the special instruction control unit, on the basis of a determination result of the instruction storage determining unit.