An optical transmission device includes an input interface unit, a cross-connecting unit, and an output interface unit, and a bandwidth switching control unit, and switches bandwidths allocated to paths in a transmission channel that connects to an adjoining optical transmission device synchronously with the adjoining optical transmission device. When the bandwidths are not continuous in the transmission channel, the bandwidth switching control unit controls the input interface unit, the cross-connecting unit and the output interface unit to rearrange the non-continuous bandwidths into continuous ones.