Abstract: The object of the invention is an inspiratory gas volume divider comprising at least two inspiratory lines (18, 19) having inspiratory branches (14,16) at ends thereof and comprising one-way valves (2,3) and at least two expiratory lines (20, 21) having expiratory branches (15,17) at ends thereof and comprising one-way valves (7,12). The inspiratory branches and expiratory branches are in pairs combined with each other in at least two inspiratory- expiratory pairs. The initial portions of the inspiratory lines are connected to the divider valve (23) provided with a control input. In the inspiratory lines, after the volume valve divider, there are included systems measuring gas volume (11,12) with output signals thereof delivered to the controller (22), and the output signal thereof is connected to the volume divider's input.