PURPOSE: To prevent a joint material from entering holes by closing an upper end of the holes in advance, and executing a joint and then opening the holes when a concrete block having thin through-holes for water drainage is laid on a road or the like.

CONSTITUTION: Through-holes 2, formed in a concrete block 1, is coated with a filler material 4 by using a spray nozzle so as to close upper ends of the holes 2. Then, the filler material 4 is leveled flat by a roller or the like. The blocks 1 are laid and sand is filled in joints and the joints are finished, and then the filler material 2 is removed to open the holes 2. A material containing sand, syrup sugar, starch capable of being plastically deformed by adding water and being dissolved by further addition of water after solidification and the like is used as the filler material 4. An adhesive tape, plugs fixed on a tape or the like are used as the filling material 4. With this method, the through-holes for water drainage can be prevented being clogged, and execution of the joints can be easily performed.