To reduce the buffer quantity of a whole device required for fluctuation absorption, even if the number of the multiple channels of inputted voice channels becomes large by separating voice cells into short cells for the respective channels after intra-network of the voice cells is absorbed and absorbing the multiplex fluctuations of the short cells of the respective channels.

A cell fluctuation absorption buffer 602 accumulates reception cell data 10a, 10b... of cell input in an inputted order, reads head reception cell data 10a after an additional delay time has elapsed and reads reception cell data 10b... at prescribed time intervals. Reception cell data 10a and 10b are dissolved into short cells 11a, 11b... for the respective channels, are sequentially accumulated in respective channel fluctuation absorption buffers 605, and data are read similarly as for the buffer 602. Thus, it is not necessary to provide the intra-network fluctuation absorbing buffer 602 with a large buffer quantity and the buffer quantity of the overall device can be reduced.