Abstract: In a cell exchange, cell diagnosis of continuity with respect to an individual part operating in a band width for a speed faster than a cell feeding speed is enabled by using cell test equipment with a low cell feeding speed. The method of cell diagnosis of continuity for this purpose comprises a step of setting a plurality of paths between a diagnosed unit to which the cell diagnosis of continuity is applied and the cell test equipment; a step of almost substantially concentrating cells sent from the cell test equipment through a plurality of paths at the diagnosed unit; and a step of returning cells concentrated at the diagnosed unit to the cell test equipment via one of a plurality of paths.