The present invention relates to a method by which a base station connected to a terminal through a first cell constructs a multi-cell network with another base station supporting a second cell, the method comprising the steps of: setting up a group including the first and second cells with the other base station through a first interface; and negotiating with the other base station through the first interface with respect to a configuration for additionally connecting the second cell to the terminal. However, the present invention is not limited to the example and other examples are possible.