PURPOSE: To efficiently obtain the subject compd. without breaking substituents on a siloxane by bringing a specified chlorosilane into contact with a specified alcohol in the presence of SeO2.

CONSTITUTION: A chlorosilane expressed by formula I is brought into contact with an alcohol expressed by R'OH (R' is a 1 to 12C alkyl) in the presence of SeO2 for an enough time at 15 to 35°C to obtain compds. expressed by formulae II to IV or a mixture of these. In formula I, R is H, phenyl, a 1 to 6C alkenyl, a 2 to 30C alkyl, etc.; x" is 0 to 2; y" is 1 to 3; (4-x"-y") is 1 to 2. In formulae II, IV, (x) is 0 to 2; (y) is 1 to 3; (x+y)≤3. In formulae III, IV, x' is 0 or 1; y' is 1 or 2; (x'+y')≤2; (m) is 3 to 10; (n) is 1 to 25. The amt. of SeO2 used is preferably 1.8 to 2.5 wt.% of the whole reaction weight.