This adhesive comprises a condensed resin having a structural unit obtained by condensation polymerization of polymerizable monomers, which include a monomer (A) having at least two carboxyl groups and a monomer (B) having at least two amino groups, wherein the adhesive satisfies at least one of (1) and (2), and satisfies (3) below. (1) At least one type selected from the group consisting of the monomer (A), an anhydride of the monomer (A), and the monomer (B) is in liquid form at 25 DEG C. (2) The condensed resin has a polyoxyalkanediyl group. (3) The condensed resin has a cyclohexane ring.