In a case in which through an Internet, a first exchange system to which a multi-functional telephone of a conference organizer who organizes a conference is connected and a second exchange system to which are connected multi-functional telephones used by conference participants who participate in the conference straddling different bases are connected, when the multi-functional telephones of the plurality of conference participants who participate in the conference are connected to the same exchange system as the second exchange system, in a video conference mixing device in the second exchange system, conference communication information (video image information+audio information) from the multi-functional telephones is previously mixed to be edited into one conference communication information, and the one conference communication information is transmitted to the video conference mixing device in the first exchange system of the conference organizer side.