PURPOSE: To produce an oligosaccharide containing panose, etc., by the fermentation.

CONSTITUTION: This method for producing an oligosaccharide by the fermentation comprises the steps of inoculating a yeast, belonging to the genus Debaryomyces and having the ability to produce the panose, preferably Debaryomyces hansenii into a culture medium consisting essentially of maltose as a carbon source, aerobically culturing the yeast, producing and accumulating the panose, etc., in the culture medium and collecting the resultant panose, etc.