PURPOSE: To enhance the efficiency of executing works of constructing a water- cut screen, ensure a high safety, suppress the costs, and perform works with high accuracy by providing possibility of continuous excavation of trench and continuous setting of seamless screen.

CONSTITUTION: To a working face 12', continuous excavation of trench 1' is made using a saw type cutter 14, and an endless water-cut screen 9' of seamless type paid off from a bobbin 16 is fed with the aid of a guide bar 17 and set stretching in the longitudinal direction of the trench 1' upon a direction change at a right angle. Fluid type retaining bags 18, 18... are inserted into the trench 1' at a certain pitch to provide timbering so that collapse is prevented, and works of water-cut screen 9' are executed continuously. This enables continuous execution of works for trench and screen, prevents collapse, permits completion of accurate works within the specified term, ensures safety, suppresses the costs, and presents a large reliability.