Here we report the characteristics of protein-polymer nanobiocomposite films and their solid state devices. The protein-polymer nanobiocomposite films (thickness = approximately 125 nm) were prepared by spin-coating the solution of cytochrome c (cyt c) and poly(vinyl alcohol) (PVA) (cyt c:PVA = 3:1 by weight). To understand the characteristics of the cyt c-PVA films (nanolayers), we employed the optical absorption and surface morphology measurement and then fabricated planar diode-type solid state devices. The optical absorption measurement showed that the heme part of cyt c in the cyt c-PVA nanolayer was well kept after the coating process, while the crack-like surface was found from the atomic force microscopy measurement. The planar device showed an ohmic type dark current, but the current gradually increased as the incident light intensity increased. In particular, the (photo) current was strongly dependent upon the voltage, which was assigned to the insulating role of cyt c surrounding groups and PVA. This trend was supported by the slow rise and decay time via photo-switching experiment.