Marihuana is produced from Cannabis sativa L.(Cannabinaceae) and called variously as haschisch, bengh, antabamik, muraba, and so on in the world. Marihuana contains typical alkyl phenolics named as cannabinoid. Among them tetrahydrocannabinol(THC)is the most strong hallucinativelly active cannabinoid. Biosynthetic enzymes of cannabinoids like tetrahydrocan-nabinolic acid synthase(THCAsynthase) has been purified and isolated from the fresh Cannabis plant and its characterization has become evident. THCAsynthase can catalyze the formation of cyclic ring of THCA from cannabigerolic acid(CBGA). Since THCAsynthase no need any co-factor like FAD, NADP NADP and FMN, it seems to be that THCAsynthase itself has co-factor in a molecule. THCAsynthase gene was cloned and super expressed using insect cell system resulting in crystallization. X-ray analysis of THCAsynthase has been succeeded to make evident its whole structure. It became evident that THCAsynthase posses FAD conjugated with histidine and systeine as a co-factor and tyrosine residue in a pocket functions as an acceptor of hydrogen from a hydrogen oxide in CBGA. Granular hair of Cannabis plant accumulated THCA because THCAsynthase was biosynthesized and expressed in only granular hair.