To improve efficiently in use and ultimate land usability of a waste disposal site and its demolished land by putting the disposition of covering layers consisting of biodegradable materials on waste deposition layers one after another.

A cave-like waste disposal plant of a depth of several to several tens meters from the ground surface is formed. The base and faces of slopes thereof are covered with impervious sheets to form an impervious layer 1. Further, the base is provided with a cover soil layer 2 to protect the impervious layer 1. A drain part 3 laid and packed with gravel, etc., is formed and a perforated pipe 5 is embedded at its center to drain water. Simultaneously, air is taken in to put the waste deposition layers A1 to A6 into a quasi-aerobic state. The circumference of the hole of the disposal plant is provided a water impermeable perpendicular impervious layer 6 arriving at a viscous soil layer N to prevent sewage leakage. The waste deposition layers A1 to A6 and covering layers B1 to B6 consisting of the biodegradable film forming materials, such as starch, are repetitively deposited successively from the bottom side at a specified thickness. As a result, the wastes are successively biodegraded and are finally completely degraded. The use rate of the disposal plant is thereby made nearly about 100%.