To maintain the proper infiltration of rainwater into the underground and prevent the subsidence of the ground by applying the constitution that honeycomb type brick tiles having many cell holes are laid so as to keep the cell holes along a longitudinal direction, and the rainwater is made to infiltrate via the cell holes.

Many cell holes 1a are formed into honeycomb shape along a longitudinal direction on a brick tile 1 made through a process where clay is extrusion molded, cut to a prescribed dimensional form, dried and baked. When brick tiles 2 and 3 similarly formed are laid in combination around the brick tile 1 laid with the cell holes 1a arrayed along a longitudinal direction, a rainwater passage can be formed out of cell holes 2a and 3a communicated with each other via the brick tiles 2 and 3. Rainwater, therefore, flows through the cell holes 1a and 2a, and properly infiltrates the underground from the surface of the ground. According to this construction, the rainwater can be kept as underground water, thereby preventing the subsidence of the ground.