The present invention provides a pressure-sensitive adhesive composition which contains a sufficient amount of an isocyanate-based crosslinking agent and is suitable for producing pressure-sensitive adhesive sheets that are less apt to cause a depression and that have improved durability. This pressure-sensitive adhesive composition comprises a (meth)acrylic polymer (A), an isocyanate-based crosslinking agent, the amount of which is at least 2 parts by weight per 100 parts by weight of the (meth)acrylic polymer (A), and a peroxide-based crosslinking agent. The amount of the peroxide-based crosslinking agent is, for example, 0.01-5 parts by weight per 100 parts by weight of the (meth)acrylic polymer (A).