PURPOSE: To improve workability by preventing water with liquid-like water- proof agent from being generated on a subbase course surface, to connect concrete slabs laid via elastic separating members arranged to be separated from the sections adjacent to each other, of the concrete slabs, and by injecting fillers.

CONSTITUTION: A subbase course R is sprayed to be disseminated or is coated with the liquid-like water-proof agent of asphalt system, and a water-proof surface course 1 is formed. After that, connecting caverns 5, 5a opening at the adjacent ends of concrete slabs P are butted to each other, and a connecting steel rod 4 is advanced to a confronting side by half the length, and through respective injecting holes 3a, the caverns 5, 5a are filled up with fillers, and the slabs P are connected to each other. After that, by using the square rods or the like of elastic rubbers, on the lower surfaces of the slabs P, elastic separating members 2 are arranged in crossed shapes and are bonded, and on the upper surfaces, filler injecting holes 3 are opened at arbitrary position. Then, the fillers are injected, through the holes 3.