PURPOSE: To obtain stabilized the coal oil mixture having high quality continuously with preventing the unevenness of the amount of a stabilizer added, by providing a feed opening for feeding a stabilizer midway in a pipe for sending the coal oil mixture, setting a reservoir part for dispersing the stabilizer in the inner part of the pipe in the lower course of the feed opening.

CONSTITUTION: A feed opening for feeding stabilizer is provided midway in a pipe for sending the coal oil mixture, and a reservoir part having a retention time at least longer than the retention time of the pulsation of a constant delivery pump in the lower course of the feed opening. The stabilizer fed from the feed opening to the the coal oil mixture is dispersed in the reservoir part, introduced to a stirring tank, and stirred by a stirring machine, to give the desired the coal oil mixture continuously.