At least one exemplary embodiment is directed to an image transmission apparatus connected to an image pickup apparatus and configured to transmit an image picked up by the image pickup apparatus to a plurality of client terminals via a network. The image transmission apparatus includes a setting unit configured to set a transmission processing mode for transmitting a still image picked up by the image pickup apparatus and a real-time image picked up by the image pickup apparatus and having a resolution lower than that of the still image according to an instruction issued from one of the plurality of client terminals, and a control unit configured to control an instruction to the image pickup apparatus and a transmission processing for the still image and the real-time image according to the transmission processing mode set by the setting unit.