An image forming system comprising an information terminal device and a printing device that is connected to the information terminal device through a network and a local connection and performs a printing process of image data sent from the information terminal device, in which the information terminal device includes a network identifier acquisition unit that obtains through the local connection a network identifier of the printing device on the network at the time of the local connection between the information terminal device and the printing device, and a data communication unit that performs data communications with the printing device through the network according to the network identifier obtained by the network identifier acquisition unit.