PURPOSE: To obtain the optical buffer device for the optical ATM switch in which a switching speed is not increased regardless of a link number with respect to the optical buffer used for the optical ATM switch.

CONSTITUTION: This buffer device is provided at an output stage of n×n optical ATM switches and is constituted of a cell distribution switch 20 receiving n-sets of inputs and distributing the inputs into r-sets of outputs and with a cell input output changeover switch 21 provided to r-sets of output lines of the cell distribution switch 20, and an optical fiber delay line 22 connecting to the cell input output changeover switch 21 and a coupler 23 receiving an output from each cell input output changeover switch 21 and coupling the outputs to one outgoing link.