An apparatus and method for detecting foam on a liquid surface in a vessel is presented. The vessel has an upper opening surrounded by a border. The vessel can be a tube-shaped. At least one image is taken from a region suspected to contain foam in the vessel by using an image sensing device that provides corresponding image data. An automatic evaluation of the image is performed on the basis of the image data by a data processing system using an image evaluation program. The at least one image is taken from the top of the vessel through the open upper opening onto the liquid surface. The image evaluation program of the data processing system identifies foam areas and non-foam areas in the image and provides information about the presence or absence of foam areas in the image as a result of the image evaluation.