The present invention is constituted of a curable composition which comprises, as essential components, the following four components:

(A) a vinyl polymer having at least one hydrosilylatable alkenyl group within the molecule,

(B) a hydrosilyl group-containing compound,

(C) a hydrosilylation catalyst, and

(D) an aliphatic unsaturated bond-containing compound, and which may further comprise

(E) an amine compound, or

the following three components:

(A) a vinyl polymer having at least one hydrosilylatable alkenyl group within the molecule,

(B) a hydrosilyl group-containing compound, and

(G) an organic compound having at least one hydrosilylatable alkenyl or alkynyl group within the molecule [other than the above-mentioned component (A)], or

the following three components:

(A) a vinyl polymer having at least one hydrosilylatable alkenyl group within the molecule,

(B) a hydrosilyl group-containing compound, and

(H) carbon black.