Provided is a curable composition excellent in curability and mechanical properties as well as a cured product thereof. Specially provided is a curable composition containing a vinyl-based polymer (I) having one or more crosslinkable functional groups at a terminus on average and a nucleophilic agent (II) and a cured product obtained by curing the curable composition. Preferably, the curable composition of the invention further contains an epoxy resin (III).