PURPOSE: To obtain a liquid ultraviolet-curing organopolysiloxane composition, comprising a linear organopolysiloxane having (meth)acryloyloxy at each terminal, a specific diorganopolysiloxane and a photopolymerization initiator and capable of providing an elastic body improved in mechanical strength.

CONSTITUTION: This composition comprises (A) a linear organopolysiloxane, containing a group selected from (meth)acryloyloxy at each terminal and having ≤100000cP viscosity at 25°C (e.g. an organopolysiloxane expressed by formula I), (B) a diorganopolysiloxane, expressed by formula II [R1 is a group expressed by formula III (R3 is a bivalent hydrocarbon; R4 is H or CH3) or methyl; R2 is a group expressed by formula III; (m) and (n) each is a positive integer satisfying [(m)+(n)]≥10 and O.05≤(m)/[(m)+(n)]≤0.5] and having ≤100000cP viscosity and (C) a photopolymerization initiator (e.g. benzoin isobutyl ether). The amounts of the components are preferably 10-100 pts.wt. component (B) based on 100 pts.wt. component (A) and 1-5wt.% component (C) based on the total weight of the components (A) and (B).