A data conversion device includes a receiving unit that receives first data and second data, transmitting after a start of the first data, transmitted from the first device to the second device, a transmitting unit that transmits the received first data and second data to a third device, and a control unit that controls a time point of transmitting the second data from the transmitting unit to lengthen a time interval between transmission of the first data and second data from the transmitting unit than a first time interval between transmission of the first data from the transmitting unit and reception of response data to the first data by the receiving unit when the first time interval is longer than a time interval between the transmission of the first data and second data from the first device to the second device.