PURPOSE: To obtain the subject compound having high purity, while suppressing side reactions, by reacting an organopolysiloxane partially having an amino group with phosgene in the presence of a basic substance.

CONSTITUTION: An organopolysiloxane containing a primary amino group in the molecule and represented by formula I (R1 is 1-8C monovalent organic group; R2-R4 are 1-8C monovalent organic group, siloxy; n is 1-10; a is 0-20) [e.g. 3aminopropyltris(trimethylsiloxy)silane] is reacted with phosgene in the presence of a basic substance (e.g. triethylamine)(an organic solvent such as n-pentane is preferably used) to provide the objective compound of formula II. The reaction temperature is preferably -30 to +10°C.