An object of the present invention is to provide a curable composition which is made mainly of a polymer having one or more reactive silicon groups, has good curability even when filler is used while a non-organotin catalyst is used, and is further high in industrial practicability. The object is solved by a curable composition, comprising, as constituents, a polymer (A) having one or more reactive silicon groups on average per molecule thereof, the reactive silicon group(s) being (each) a group which can be crosslinked by forming a siloxane bond, a Lewis acid and/or derivative thereof (B), an amine compound (C), a compound (D) having a reactive silicon group, and filler (E), and obtained by mixing the constituents with each other.