The photoinduced electron transfer rate in hetero Langmuir-Blodgett (LB) films composed of 7,8-dimethyl-10-dodecyl isoalloxazine (flavin) and N-docosylquinolinium tetracyanoquinodimethan (TCNQ) was investigated. Flavin and TCNQ were used as electron donor and acceptor, respectively. The time-resolved fluorescence decay of three different types of flavin/TCNQ hetero LB films such as mixed layer, head (hydrophilic functional group)-to-head interfaced structure and tail (hydrophobic alkyl chain)-to-tail interfaced structure were measured by a time-correlated single photon counting (TCSPC) method. Electron transfer rate from photoexcited donor to acceptor depends on the distance between functional groups, since the fluorescence decay of head-to-head interfaced hetero LB films occurs faster than that of tail-to-tail interfaced hetero LB films. Based on the faster electron transfer of flavin/TCNQ hetero LB films than that of flavin/viologen hetero LB films, the redox potential difference between donor and acceptor affects the charge transfer rate.