Diarylethenes were obtained from the corresponding ethenyl sulfones by photocatalyzed desulfonylation using UV or blue LEDs. When perylene and i-Pr2NEt were used as a photocatalyst and a sacrificing reagent, respectively, this desulfonylation proceeded smoothly to afford the desired ethenes with the functional groups such as chloro, alkoxy and heteroaromatic rings remaining untouched. The use of a flow photoreactor enabled this desulfonylation to proceed more rapidly to finish in an hour of residence time.