The present invention relates to a pressure-sensitive adhesive composition used for a pressure-sensitive adhesive sheet to be directly attached to a metal surface, the composition including, as a base polymer, an acrylic copolymer obtained by polymerizing a monomer mixture, the monomer mixture including: at least one monomer (monomer ml) selected from alkyl (meth)acrylates represented by the formula (I): CH 2 =C(R 1 )COOR 2 in which R 1 is a hydrogen atom or a methyl group, and R 2 is an alkyl group having 1 to 20 carbon atoms, in an amount of 50 to 99.9% by weight based on a total amount of the monomer mixture, and at least one monomer (monomer m2) selected from N-hydroxyalkyl (meth)acrylamides represented by the formula (II): CH 2 =C(R 3 )CONHR 4 in which R 3 is a hydrogen atom or a methyl group, and R 4 is a hydroxyalkyl group having 2 to 4 carbon atoms, in an amount of 0.1 to 25% by weight based on the total amount of the monomer mixture; and the monomer mixture including substantially no carboxyl group-containing monomer.