To obtain the subject compound useful as a graft-modified component for organic polymers, a component for addition polymerization, etc., in a good yield by reacting a silicon compound having a silanol group or hydrolyzable group with a vinyl group-containing organic metal reagent.

When a silicon compound having a silanol group or hydrolyzable group X (e.g. dimethyldichlorosilane) is reacted with a vinyl group-containing organometallic reagent (e.g. vinylmagnesium chloride), the silicon compound having silanol group or a hydrolyzable group X and THF are charged into a flask and THF solution of the vinyl group-containing organometallic reagent is gradually dropped from a dropping funnel equipped with a pressure equalizer into the flask and reaction of these components is carried out by heating reaction mixture under reflux of THF for 2hr to readily provide the objective vinyl group-containing silicon compound useful as a graft-modified component for organic polymers, a component, etc., for vinyl polymerization or hydrosilylation polymerization in good yield.