A solution-processed organic photoconductive device sensitive to the only blue-light was demonstrated using poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT). The spectral selectivity was good enough to divide the incident light into a blue component, indicating the possibility of color separation without a prism for video cameras in combination with green-and red-sensitive devices. The maximum conversion efficiency of 190 mu A/W was observed while irradiating the blue-light (475 nm) and applying the voltage (2.4 V). In addition, the response speed of more than 30 Hz was achieved, and it was fast enough to apply this photoconductive device to practical applications.