The invention relates to a method of separating a particle fraction from a particle stream making use of gravitational force and which is performed in a fluid. This provides particle fractions that are collected in respective collecting means. According to the invention the fluid and the collecting means are moved in relation to each other defining a relative direction of movement. There are means provided to limit the movement of the particles to be separated with respect to the fluid in the relative direction of movement. The invention also relates to an apparatus for carrying out the method.