The disclosure describes an apparatus for continuous immersion washing of pieces of fabric and more particularly of knitted fabric, which comprises a plurality of washing tanks provided with a sequence of groups of rollers, each group comprising closely spaced washing, widening and feed rollers which are arranged for guiding the progressing fabric through the liquid baths within said tanks, said rollers alternatively acting on said fabric to exert a gentle transversal and longitudinal pull to ensure complete maintenance of the fabric in its full width while being processed.