ABA block copolymer, dispersant, and pigment dispersion composition

An ABA block copolymer comprising:

• an A block containing a structural unit represented by a general formula (1) below and a structural unit derived from a vinyl monomer with an acid group;
• and a B block containing a structural unit derived from a vinyl monomer with an aromatic ring group or an alicyclic alkyl group, the ABA block copolymer having an acid value of 30 to 250 mgKOH/g,
• wherein in the general formula (1) R1 is a hydrogen atom or a methyl group and R2 is an alkyl group having 2 to 10 carbon atoms,
• the structural unit represented by the general formula (1) is at a content of 20 to 80% by mass in 100% by mass of the A block
• and wherein the content of the structural unit derived from a vinyl monomer with an acid group is, in 100% by mass of the A block, 5 to 40% by mass.