To prevent data from being illegally used at the time of transmitting/ receiving data between respective picture processors connected to a network.

A 1st image forming device is provided with plural information adding means 431 to 43n for adding specific information to picture data to be transmitted to a device terminal equipment 10 through a network 101 and an added information selection means 42 for selecting either one of the means 431 to 43n in accordance with the picture data at the time of transmitting the picture data through the network 101 and adding prescribed specific information to the picture data by the selected information adding means. Thus the security of data on the network 101 and the copyright of a data writer can be surely protected by tracing the distribution details of the picture data.