The present invention relates to a mixing device for mixing a liquid, such as water, with an instant ingredient to form a beverage. The mixing device comprises a mixing chamber and a rotor which, during rotation about the axis of rotation, defines a surface of revolution extending along the circumference of the rotor. The rotor is arranged in the mixing chamber. The mixing chamber comprises a peripheral wall zone having a substantially circular cross section. The peripheral wall zone surrounds the surface of revolution. An outlet duct for discharging the mixture formed is connected to the mixing chamber. The inlet of the outlet duct is provided at the rotor. At least one rotor rib is provided at the peripheral wall zone. This rotor rib extends from the peripheral wall zone in the direction of the surface of revolution of the rotor. The invention furthermore relates to a beverage-making device comprising a mixing device according to the invention, as well as to the use of a mixing device according to the invention.