A continuous mixer (10) comprises an elongated mixing container (11), which has an inlet opening (14) at one end for feeding in the basic components to be mixed and which encloses a mixing space (12), which merges at the other end into a discharge region (22) for the delivery of the mixed product, and in which mixing container (11) there is arranged a mixing tool (13), which is rotatable about an axis (41), is driven by a drive (18, 40) and mixes together the basic components fed into the inlet opening (14) and at the same time transports them to the discharge region (22). In such a mixer, improved control of the mixing conditions is achieved by an adjustable discharge opening (19) adjustable in size being arranged between the discharge region (22) and the mixing space (12).