A pipe for underdrainage comprises (1) a liquid-collecting pipe; (2) a plurality of discontinuous protrusions on the outer surface of the liquid-collecting pipe; (3) a filter layer capable of passing liquid while substantially excluding solids, the filter layer being disposed around the liquid-collecting pipe and contacting the top portions of the protrusions; and (4) a liquid-conducting way composed of a space communicating both in the longitudinal direction and in the peripheral direction of the liquid collecting pipe and defined by the protrusions, the outer surface of the liquid-collecting pipe and the inner surface of the filter layer.