To make it possible to drastically reduce the volume of crude refuse by adding and mixing a specific ratio of clay material-contg. slaked lime contg. clay materials to and with the crude refuse slurried by crushing, then allowing the crude refuse to cure of itself and dehydrating the crude refuse by making combination use of the sepn. of the water in the crude refuse and the transpiration of the water accompanying the progression of reaction.

In the case the crude refuse discharged from homes, restaurants, etc., is subjected to the dehydration treatment, the crude refuse is first slurried by a crushing means and 5 to 35 pts.wt. clay material-contg. slaked lime contg. 10 to 20% clay material is added and mixed to and with 100 pts.wt. the slurried crude refuse and thereafter, the crude refuse is allowed to cure of itself. The crude refuse is thus dehydrated by making combination use of the sepn. of the water in the crude refuse and the transpiration of the water accompanying the progression of reaction. The clay material-contg. slaked lime formed by using the clay materials, such as red ball earth, vermiculite and montmorillonite, as nuclei and adhering slaked lime to the circumference thereof and granulating these clay materials is used as the clay material-contg. slaked lime to be used. The separability of the water and the flocculating property of the crude refuse are improved according thereto, by which the volume of the crude refuse is drastically reduced in a short period.