A data processing device that is capable of being connected to a multiple optical axis photoelectric sensor for detecting a shielded state for each of a plurality of optical axes to output a signal indicating presence or absence of an object on the basis of a result of detecting the shielded state, and is capable of reading and writing data including setting data for setting definitions of detecting operations at the multiple optical axis photoelectric sensor, the data processing device for the multiple optical axis photoelectric sensor comprising: a communication section that is capable of communicating with the multiple optical axis photoelectric sensor; a storing section that is capable of storing the setting data and product information of the multiple optical axis photoelectric sensor; a setting section for setting operating conditions of the data processing device; and a control section for controlling an operation of the data processing device, wherein when the control section detects that the data processing device is connected to the multiple optical axis photoelectric sensor: the control section reads the setting data from the multiple optical axis photoelectric sensor through the communication section to store the setting data read from the multiple optical axis photoelectric sensor in the storing section, if the control section determines that the data processing device has a use history of the data processing device, and if the reading of the setting data is set to be enabled by the setting section, and characterized in that: the control section writes the setting data, which is stored in the storing section, in the multiple optical axis photoelectric sensor through the communication section, if the control section determines that the data processing device has a use history of the data processing device, and if the reading of the setting data is set to be disabled by the setting section, and if product information of the multiple optical axis photoelectric sensor does not coincide with that stored in the storing section, and the control section forcibly reads the setting data from the multiple optical axis photoelectric sensor through the communication section to store the setting data read from the multiple optical axis photoelectric sensor in the storing section, if the control section determines that the data processing device does not have a use history of the data processing device. a communication section that is capable of communicating with the multiple optical axis photoelectric sensor; a storing section that is capable of storing the setting data and product information of the multiple optical axis photoelectric sensor; a setting section for setting operating conditions of the data processing device; and a control section for controlling an operation of the data processing device, wherein when the control section detects that the data processing device is connected to the multiple optical axis photoelectric sensor: the control section reads the setting data from the multiple optical axis photoelectric sensor through the communication section to store the setting data read from the multiple optical axis photoelectric sensor in the storing section, if the control section determines that the data processing device has a use history of the data processing device, and if the reading of the setting data is set to be enabled by the setting section, and characterized in that: the control section writes the setting data, which is stored in the storing section, in the multiple optical axis photoelectric sensor through the communication section, if the control section determines that the data processing device has a use history of the data processing device, and if the reading of the setting data is set to be disabled by the setting section, and if product information of the multiple optical axis photoelectric sensor does not coincide with that stored in the storing section, and the control section forcibly reads the setting data from the multiple optical axis photoelectric sensor through the communication section to store the setting data read from the multiple optical axis photoelectric sensor in the storing section, if the control section determines that the data processing device does not have a use history of the data processing device. the control section writes the setting data, which is stored in the storing section, in the multiple optical axis photoelectric sensor through the communication section, if the control section determines that the data processing device has a use history of the data processing device, and if the reading of the setting data is set to be disabled by the setting section, and if product information of the multiple optical axis photoelectric sensor does not coincide with that stored in the storing section, and the control section forcibly reads the setting data from the multiple optical axis photoelectric sensor through the communication section to store the setting data read from the multiple optical axis photoelectric sensor in the storing section, if the control section determines that the data processing device does not have a use history of the data processing device.