PURPOSE: To obtain the titled drink having good taste with little feeling of foreign matter due to fibers, by reacting cellulase (or microorganism capable of producing same) with a specific milk liquid, inactivating the resultant product, adding thermophilic bacteria of the genus Thermus thereto, and fermenting the resultant mixture.

CONSTITUTION: About 0.5% cellulase (or microorganism capable of producing same) is added to a milk liquid prepared from soybeans (processed beans), and cultivated at about 40°C for about 4hr by shaking culture, and inctivated by heat treatment, etc. Microorganisms of the genus Thermus which are asporogenic bacilli having 0.5μm width and 2W3μm length, have decomposition ability for sucrose, rafginose and stachyose, etc. and grow at 40W80°C are added to cultivate the resultant mixture and give the titled drink having the desired amount of acid.