Providing a crosslinkable composition and a crosslinking agent is objected to, which are capable forming a crosslinked product that is superior in retort resistance, with suppressed bleeding out from the crosslinked product, and that has favorable interlayer adhesiveness when formed into a multilayered structure crosslinked product. The present invention provides a crosslinkable composition containing (A) a polymer having an SP value of no less than 9.5 (cal/cm 3 ) 1/2 and no greater than 16.5 (cal/cm 3 ) 1/2 , and (B) a crosslinking agent having one or more polar groups that include an oxygen atom and a nitrogen atom not constituting an aromatic ring, and two or more polymerizable groups. The difference between the SP value of the polymer (A) and the SP value of the crosslinking agent (B) is preferably no greater than 2 (cal/cm 3 ) 1/2 , and more preferably no greater than 1 (cal/cm 3 ) 1/2 . A decomposition temperature of the crosslinking agent (B) is preferably no less than 240°C, and a melting point of the crosslinking agent (B) is preferably no greater than 220°C.