Photoregulation of polymer chain scission based on a Diels-Alder (DA) adduct containing diarylethene (DAE) was investigated. Poly(epsilon-caprolactone) with a DA adduct conjugated with DAE skeleton (DAE/DA) at the center of the chain was synthesized by ring-opening living cationic polymerization of epsilon-caprolactone, initiating from diol-type DAE/DA, and its chain scission via thermally induced retro-DA reaction was successfully controlled by photoisomerization of DAE.