A silicone-based pressure-sensitive adhesive composition comprising (A) a condensation-reaction product obtained by subjecting a diorganopolysiloxane having silanol groups on both molecular terminals and 2 or more silicon-bonded alkenyl groups located in side molecular chains in one molecule (a) and organopolysiloxane resin having one or more hydrolyzable groups in one molecule (b) to a condensation reaction in the presence of catalyst (c), (B) an organohydrogenpolysiloxane, (C) a diorganopolysiloxane having silicon-bonded alkenyl groups on both molecular terminals, (D) an organopolysiloxane resin and (E) a platinum catalyst.