To provide a method for modification of waste in city waste drying facilities where the drying efficiency is increased by effectively modifying the low-quality wastes of a high water content prior to charging the wastes into a dryer to prevent that the low-quality wastes are charged into the dryer.

The method is characterized in that a supplier 2 is provided with a feed hopper 20 and a weighting conveyer 21, in that the number of revolutions of the motor for a screw conveyer 23 in the feed hopper 20 is so adjusted and controlled that a specified weight of the wastes can be positioned on the weighing conveyer 21, and in that by monitoring the number of revolutions of the screw conveyer 23 in the supplier 2 and by judging that the low-quality wastes are being charged into the dryer 1 when the number of revolutions falls below a specified number, the low-quality wastes are mixed with dried wastes returned to the supplier 2 through a return passage 6.