A silicon-containing isocyanate compound represented by the following general formula [I]: ##STR1## wherein each of R.sup.1, R.sup.2, and R.sup.3 independently represents a hydrocarbon group having 1 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or a trialkyl siloxy group (each alkyl having 1 to 4 carbon atoms), with the proviso that at least one of R.sup.1, R.sup.2, and R.sup.3 is an alkoxy group having 1 to 6 carbon atoms, and n is a number of from 1 to 4, can be obtained in a high yield by reacting carbonyl chloride with a silicon-containing alkylamine represented by the following general formula [II]: ##STR2## wherein R.sup.1, R.sup.2, R.sup.3, and n are as defined above, in an inert organic solvent in the presence of a tertiary amine. If a filtrate remaining after removal of a tertiary amine hydrochloride from the reaction liquid, a liquid remaining after removal of the solvent from the filtrate, or a distillate formed by distillation of this liquid is treated with an alkali metal salt or alkaline earth metal salt of higher fatty acid or an aromatic carboxylic acid, the intended product can be obtained at a high purity in a high yield.