Provided is a breathing-synchronized gas supply device for supplying a breathing gas in synchrony with the breathing of a user, wherein the flow rate of the breathing gas flowing through an orifice on a synchronized flow side corresponding to the set flow rate value of a flow rate setting means is divided into a plurality of groups of flow rates in a fixed ratio with respect to the set flow rate, and a control means is provided for controlling the opening and closing of an automatic opening and closing valve for the same opening time within same divisions.
