To restrict transmission by an unspecified person, and to prevent abuse by attaching sender information to transmission data.

The image forming apparatus comprises an image forming means for reading an original image and forming image data, an image transmitting means capable of transmitting the image data formed by the image formation means via a network, a certificate authentication station registration means for registering certificate authentication station information for verifying the validity of an electronic certificate, an electronic certificate input receiving means for receiving the input of the electronic certificate of a person who instructs transmission before the image data are transmitted, a verification means for verifying an owner mentioned in the electronic certificate based on the certificate authentication station information registered by the certification authentication station registration means and the electronic certificate accepted by the electronic certification input acceptance means, and a transmission authorization means for authorizing the transmission of the image data by the image transmission means based on an instruction with the certificate mention item of the person who instructs transmission as source information only when the person who instructs transmission is verified by the verification means.