PURPOSE: To easily treat night soil in a household, etc., by agitating and hashing the night soil from a stool, treating the material in a filter tank to separate water, and incinerating the residue freed of water by an incinerator.

CONSTITUTION: The night soil from the stool 10 is transiently stored in a first tank 14, and the stored night soil is agitated by agitators 16 and 18. The night soil is then sent from the first tank 14 to the filter tank 26, the water in the night soil is separated therein, and the separated water is stored in a second tank 24. The residue freed of water in the tank 26 is incinerated by the incinerator 20. The second tank 24 and a low tank 11 are connected to utilize the water stored in the second tank 24 as flush water, and the water in the second tank 24 is supplied to the low tank 11. As a result, night soil can be easily treated in a household, etc.