PURPOSE: To treat a large amount of garbage by grinding the garbage charged in a garbage container by high pressure water and dehydrating the same by the rotation of the garbage container.

CONSTITUTION: After both lids 12, 14 are closed, a drive motor 5, a high pressure water pump 23 and a power motor 28 are started simultaneously or almost simultaneously. A garbage container 4 is rotated at a predetermined number of rotations of 3000-12000rpm in a state supported at two upper and lower points and a high pressure jet water stream 19 of predetermined pressure are jetted to the inner peripheral surface of the garbage container from the nozzle orifices 18a of a high pressure water nozzle 18. The high pressure jet water stream 19 are uniformly jetted to the garbage in the garbage container 4 to finely break the garbage in to pieces. The moisture in the garbage and the high pressure jet water streams 19 are removed by the high speed rotation of the garbage container to be discharged to the outside.