The present invention relates to a device for frothing up a liquid, in particular cold and/or unheated milk, having a liquid supply line for supplying the liquid, an air supply line which opens into the liquid supply line for supplying air into the liquid, a discharge line which is configured downstream of the opening of the air supply line into the liquid supply line for discharging the mixture of liquid and air, a first conveying unit, in particular a pump, which is provided for conveying the liquid through the liquid supply line and/or the mixture through the discharge line and a mixing unit which is provided downstream of the opening in the discharge line, the mixing unit including at least one narrow place or being configured as narrow place of the discharge line.