An image forming apparatus, comprising: a first control means ; a second control means that is connected to a load , and is adapted to control the load based on an instruction from the first control means ; a first communication line adapted to transmit data from the first control means to the second control means ; and a second communication line adapted to transmit data from the second control means to the first control means , wherein the second control means comprises: a holding means for holding data; and a processing means for transmitting a return to the first control means by using the second communication line when receiving the instruction from the first control means via the first communication line , and for transmitting the data held in the holding means to the first control means based on a set period by using the second communication line , characterized in that wherein the processing means is adapted to delay a timing for transmitting the data held in the holding means based on a state of the reception of the instruction from the first control means via the first communication line and a state of the return using the second communication line at the timing for transmitting the data held in the holding means based on the set period, so that the transmission of the data held in the holding means is prevented from overlapping the transmission of the return, wherein the instruction from the first control means includes a write instruction and a read instruction, wherein the read instruction includes radded dummy data, and wherein the length of the read instruction does not become shorter than the length of transmission data which the processing means transmits to the first control means based on the set period. a first control means ; a second control means that is connected to a load , and is adapted to control the load based on an instruction from the first control means ; a first communication line adapted to transmit data from the first control means to the second control means ; and a second communication line adapted to transmit data from the second control means to the first control means , wherein the second control means comprises: a holding means for holding data; and a processing means for transmitting a return to the first control means by using the second communication line when receiving the instruction from the first control means via the first communication line , and for transmitting the data held in the holding means to the first control means based on a set period by using the second communication line , a holding means for holding data; and a processing means for transmitting a return to the first control means by using the second communication line when receiving the instruction from the first control means via the first communication line , and for transmitting the data held in the holding means to the first control means based on a set period by using the second communication line , characterized in that wherein the processing means is adapted to delay a timing for transmitting the data held in the holding means based on a state of the reception of the instruction from the first control means via the first communication line and a state of the return using the second communication line at the timing for transmitting the data held in the holding means based on the set period, so that the transmission of the data held in the holding means is prevented from overlapping the transmission of the return, wherein the instruction from the first control means includes a write instruction and a read instruction, wherein the read instruction includes radded dummy data, and wherein the length of the read instruction does not become shorter than the length of transmission data which the processing means transmits to the first control means based on the set period. <EOS>