A gas mixer for mixing a first gas and a second gas, including a gas housing, a Venturi tube, a flow body for the first gas arranged in the Venturi tube to form a mixing gap, an inflow tube connected to the Venturi tube, to an inflow opening to the Venturi tube for the second gas, and an actuating element for varying the inflow cross section of the inflow opening. The actuating element has a first and a second actuating part which restrict the inflow cross section. The first actuating part is a first gas housing part and the second actuating part is a second gas housing part. At least one of the gas housing parts forms part of the Venturi tube and/or of the inflow tube At least one of the gas housing parts can be moved with respect to another and has a rotor of a linear motor.