Pressure-sensitive adhesives for optical films exhibit high cohesion, excellent re-workability, adhesion properties, heat resistance and durability without chemical crosslinking.A pressure-sensitive adhesive contains an acrylic triblock copolymer (I) at not less than 60% by mass based on the total mass of all solids contained in the pressure-sensitive adhesive, the acrylic triblock copolymer being represented by the formula A1-B-A2 wherein: A1 and A2 are each independently an alkyl methacrylate polymer block having Tg of not less than 100° C. and B is an acryl acrylate polymer block having Tg of not more than −20° C.; the content of the polymer block B is 50 to 95% by mass; Mw is in the range of 50,000 to 300,000; and the molecular weight distribution is in the range of 1.0 to 1.5. In a preferred embodiment, the acrylic triblock copolymer (I) is a combination of an acrylic triblock copolymer (Ia) having Mw of 50,000 to less than 100,000 and an acrylic triblock copolymer (Ib) having Mw of 100,000 to 300,000, in a mass ratio (Ia):(Ib) of 45:55 to 75:25.