Abstract: Disclosed is a novel modified organopolysiloxane compound characteristically having carboxylalk(en)ylcarbonyl groups substituting for the hydrogen atoms on the N atoms in an aminoalkyl group-containing organopolysiloxane as introduced by the reaction of a dicarboxylic acid anhydride such as maleic anhydride and succinic anhydride with an aminoalkyl group-containing organopolysiloxane. This modified organopolysiloxane compound serves as a principal ingredient in an aqueous emulsion composition for a finishing treatment of various fabric material to impart excellent touch feeling of softness to the fabric material with little problem of yellowing of the fabric material unavoidable with conventional aminoalkyl group-containing organopolysiloxane compounds. The inventive modified organopolysiloxane compound in the form of an aqueous emulsion is also useful for a waterproofing treatment of paperboards for plasterboards to serve as a covering sheet on the core board of hydrated gypsum.