We have developed a direct photosynthetic/metabolic biofuel cell (DPBFC) without a mediator, based on the extraction of electrons directly from bacteria using a polyaniline electrode. Since previous developments of this nature are rigid, they are not suitable for use on curved or soft surfaces. Our DPBFC has a flexible structure due to its flexible components: a membrane electrode assembly made of Nafion 117, a carbon cloth electrode made of modified polyaniline, a copper foil current collector, an anode chamber made from molded polydimethylsiloxane (PDMS), and a cathode chamber and cover cut from a PDMS membrane. Silicone bonds were used for assembling the individual parts. Our 50×50×3-mm flexible DPBFC has a stable electrical power output up to a bending angle of 170°. The maximum power density using purple photosynthetic bacteria (Rhodopesudomonas palustris) as a fuel source was 5.26μW/cm2 with an open-circuit voltage of 0.089 V.