PURPOSE: To provide a water stopping material capable of improving workability for stopping water, preventing a water stopping agent from flowing to a foundation, and maintaining a long-term water stopping effect.

CONSTITUTION: Water permeable sheet materials 5a and 5b are pasted to the front and reverse sides of a bulky and long network mat 2 formed with synthetic polymer continuous filaments 21b having a diameter of between 0.5mm and 1.5mm. Also, the gaps of the mat 2 are lamellarly filled with a water stopping agent 7 for sealing. Furthermore, at least one of the sheet materials 5a and 5b is extended from a both-end bonded section externally to form a water stopping material 1 having a jointing lug section 11. In executing a construction work for water stopping, the lug section 11 is overlaid on the side edge of an adjacent water stopping material 1, and the overlaid section is filled with a water stopping agent 7A, thereby preventing water leakage at the joint section of the water stopping materials 1 and 1.