Biomaterials should have some required performances such as mechanical properties and biocompatibility. From the viewpoint, they have been investigated so far. However, an important factor has been missing in some cases. That is the infection resistance. And the final one is related closely to the biofilm and its control. In this experiment, we focus on graphene, an advanced material. The graphene has many high performances and biocompatibility. From the viewpoint, it may get a chance to be applied to biomaterials. However, our prelimnary experiments showed that graphene has its high sensitivity to resident microbiota and tended to form biofilms easily. Since resident microbiota form complicated flora composed of plural bacteria, it is very hard to tell which bacterium formed biofilm mainly. However, it would be very important to investigate the biofilm formation capability by a certain bacterium, when we come to think about the applicability to biomaterials. In this experiment, we chose E.coli as gram negative bacterium and S.epdermidis as gram positive one, since both cause infections and chronic diseases in our human bodies very often. Graphene was prepared by CVD (Cemical Vapor Deposition) and mechanical methods (tape-detachment process). The specimens were measured and the formation of graphene was confirmed by a Laser Raman Spectroscopy. The specimen was set in spme kinds of laboratory biofilm reactors (LBRs) which we have developed in our loboratory. LBRs were filled with liquid cultures including target bacteira. The test continued in a couple of days at a certain temperature (25 degrees Celsius for E.coli and 37 degrees Celsius for S.epidermidis.) After the immersion test in those LBRs, biofilms on graphene samples were observed and measured by Raman Spectroscopy, staing by crystal violets and optical microscopic observations. The results were compared, analyzed in various cases and the applicability of the advanced material to biomaterials and human bodies was discussed.