PURPOSE: To prepare a photo-curing type pressure sensitive adhesive requiring no solvent by comprising polysiloxane consisting of resin type polysiloxane, in which a diorganoalkenylsiloxy group and a diorganohydrosiloxy group are provided as terminal groups, and a curing catalyst.

CONSTITUTION: A pressure sensitive adhesive composition is composed of (A) benzene soluble polysiloxane having a triorganosiloxy group and a SiO4/2 units, (B) alkenylsiloxy terminal closed diorganopolysiloxane indicated by formula I [respective R4 independently represent alkyl groups and aryl groups while 70% or more of R4 and CH3 groups; (x) represents a number ranging from 0 to 150 (15-50, desirably); (n) represents a number ranging from 0 to 16], (C) diorganohydrosiloxy terminal closed diorganopolysiloxane indicated by formula II [respective R5 independently represent alkyl groups and aryl groups while at least 70% of R5 are CH3 groups; (y) represents a number ranging from 0 to 1000 (15-50, desirably)], (D) an organic silicon compound having two or more groups reactive with the H group or the alkenyl group in polysiloxane, and (E) a hydrosilylation curing catalyst. In the pressure sensitive adhesive composition, a mixing ratio of the substance A to the substances B+C+D is 50-65 parts to 50-35 parts.