Abstract: The present invention concerns a shut-off valve comprising a valve body provided with at least two passage ports and a shut-off member of the passage ports with its operating shaft rotatably carried in the valve body, said shut-off member being connected with the operating shaft by means of an arcuate member, which rests against a staying member on the bottom of the valve body and is elastic, in such manner that the shut-off member may be shifted from one passage port to another by turning the operating shaft, whereby the shut-off member is pressed against the inner surface of the valve body, radially urged by the arcuate member. The valve comprises an adjustable tensioning means, against which the arcuate member is braced and by adjustment of which the pressure of the shut-off member against the inner surface of the valve body is adjustable with change of the curvature of the arcuate member.