A silicone-based pressure-sensitive adhesive comprising: (A) a mixture or a product of partial condensation of (a) a raw rubberlike organopolysiloxane having an average of at least one alkenyl group per molecule and (b) an organopolysiloxane resin consisting essentially of R13SiO1/2 units and SiO4/2 units; (B) an organopolysiloxane having an average of at least two silicon-bonded hydrogen atoms per molecule; (C) a phenol-type oxidation inhibitor and/or a phenol-modified organosiloxane; (D) an aromatic amino-type oxidation inhibitor and/or aromatic amino-modified organosiloxane; and (E) a platinum-based catalyst, can form a pressure-sensitive adhesive layer that maintains good removability after being exposed to high temperatures.