Abstract: Provided is an organopolysiloxane compound acting as a chain extender for use in a room-temperature-vulcanizing (RTV) composition of a dealcoholization type that can be rapidly turned into a rubber and then exhibit a rubber elasticity. The organopolysiloxane compound is represented by the following general formula (1), and also provided is a composition containing this compound and a linear diorganopolysiloxane with both molecular chain ends being blocked by a silanol group or a hydrolyzable silyl group, wherein each of R1, R2, R3 and R4 independently represents a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms; and n is a number of 0 to 10.