The present invention relates to a technique by which a line in a trunk group is selected within an exchange such as an ATM exchange that handles cells with fixed lengths. The object is to obtain a multiple effect in a burst traffic to realize a communication state with good efficiency. The device, that selects a line in a trunk group within an exchange that handles cells with fixed lengths, includes a similarity deciding unit that decides the similarity of a burst characteristic of an input signal, and accommodating line deciding unit for deciding an accommodating line in accordance with a result decided by the similarity deciding unit.