To provide a method of constructing a water barrier structure which enables construction with a relatively small construction machine and coping well with conditions associated with a narrow construction yard and improves the water barrier performance and the construction efficiency and reduces the costs associated with joints by arranging a long water barrier sheet to reduce joints of the sheet.

The method comprises plowing ground in groove form to replace with a fluid S and arranging a water barrier sheet 4 in the groove 3 replaced with the fluid S and has an insertion process of inserting a rolled water barrier sheet 4 into the groove 3 and an extension process of extending the rolled water barrier sheet 4 in the groove 3.