Provided is a curable composition in which the solubility in a solvent (in particular, water) is high and in which properties of a cured film obtained using the curable composition stored for a predetermined time are superior. The curable composition includes: a compound A represented by Formula (A) and at least one compound X selected from the group consisting of compounds represented by Formulae (X1) to (X4), in which a content of the compound X is 0.01 to 2.0 mass % with respect to a total mass of the compound A and the compound X; or a compound B represented by Formula (B) and a compound Y represented by Formula (Y), in which a content of the compound Y is 0.01 to 2.0 mass % with respect to a total mass of the compound B and the compound Y.