A pyridonecarboxylic acid derivative or a salt thereof is represented by Formula (1), where R1 is hydrogen, a halogen atom, a lower alkyl group, or an amino group； R2 is —；NH—；R6, where R6 is hydrogen, a lower alkyl group, an amino lower alkyl group, or the like； —；O—；R7, where R7 is hydrogen, a lower alkyl group, or the like； —；(CH2)m—；R8, where R8 is an amino group or the like, m is 1, 2, 3 or 4； or a cyclic amino group of Formula (2), where Y represents NH or C—；R9aR9b, where R9a and R9b are each independently hydrogen, a lower alkyl group, an amino group, a lower alkyl amino group, or the like； n and p are 1 or 2； R3 is hydrogen, a halogen atom, a lower alkyl group, or the like； R4 is hydrogen or a carboxyl group-protecting group； and R5 is hydrogen or a hydroxyl group-protecting group.
