To facilitate picture transmission in real time through the use of a general-purpose compressed chip in a picture transmitter transmitting a picture in real time by utilizing a network in a variable network.

Through the use of compression by each picture block of 8×8 pixels in a JPEG compression system, on the side of a server 11 a compressed picture block selecting part 113 extracts only a compressed block to be a reducing object from a compressed picture and a transmission part 114 transmits it. On the side of a client 12, at the time of extending a received block, a DC component extraction part 123 extracts only a DC component to make this one pixel of a reduced picture. A reduced picture generation part 125 combines respective reduced pixels to make the reduced picture. When the server sends the reduced picture to the client, an already transmitted picture is not transmitted and when the client expands the received picture an already expanded picture is not expanded to reduce the loads on processing at the server and the client.