A control apparatus configured to receive instruction data from a transmission unit and to control a controlled apparatus based on the instruction data includes a determination unit configured to determine an error in reception of the instruction data from the transmission unit, a communication unit configured to receive the instruction data from the transmission unit and to transmit reply data according to a result of determination of the determination unit to the transmission unit, a module configured to control the controlled apparatus based on the instruction data, and a control unit configured to, if a content of current instruction data received by the communication unit matches a content of previous instruction data received by the communication unit, control the module not to control the controlled apparatus based on the current instruction data.