A gas laser system including a laser oscillator including a device which needs a predetermined standby time until normally starting an operation after stopping an operation due to reduction of a power supplied from a power source unit, a controller, a power reduction detection unit, and a nonvolatile storage unit storing time data of a first time point when the reduction of the supplied power is detected by the power reduction detection unit. The controller calculates an operation stop time of the device, based on time from the first time point to a second point time when a next system activation command is output, and inhibits operation resumption of the device when the operation stop time is within a predetermined standby time.