Electrical carrier separation from a photoexcited photochromic molecule could be a promising method for controlling the photosensitivity of such a molecule. We report an efficient carrier separation from a photochromic diarylethene (DAE) molecule by adopting a device structure with a heterojunction consisting of an n-type diarylethene layer and a p-type layer of N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine (NPB). A photocurrent originating from carrier separation for the colored photostationary state was observed, even at zero applied voltage. The efficient carrier separation occurred at the interface between the DAE and NPB layers and was the result of the internal electrical field induced by the pn heterojunction.