PROBLEM TO BE SOLVED: To provide a construction method for underground waste water treatment facilities, which is suitable for a road and the like within facilities such as a park.SOLUTION: A construction method of this invention makes rainwater flow down by forming an infiltration layer 11, which allows infiltration of the rainwater from above, and a drainage layer 12, which comprises one or more drainage parts 13 having an inclined gradient in a flow direction, below a permeable base course. The construction method includes a first step of disposing a water flowing structure 1, in which the infiltration layer 11 and the drainage layer 12 are pre-integrated together, in a surface layer of ground GB while providing an inclined gradient in a lengthwise direction, and a second step of forming the permeable base course I on its surface.
