Diarylethene is one of the promising photo responsive deforming materials, which can be used in various fields of applications due to their thermal stability, fatigue resistance, and high sensitivity. As the photo responsive reaction of diarylethene unimolecule is directly changing crystal structure of the diarylethene, knowing optical reaction of a diarylethene molecule is crucial factor in predicting its geometrical change. For this reason, the present study mainly focuses on its goal in understanding photo-response quantum path of diarylethene unimolecule by performing DFT-based simulations. We develop diarylethene molecule model, and find conical intersection which is the unknown state in photo-response quantum path in this paper.