Room temperature light emission from Ge self-assembled quantum dots (QDs) embedded in L3-type photonic crystal (PhC) nanocavity is successfully demonstrated under current injection through a lateral PIN diode structure. The Ge QDs are grown on silicon-on-insulator (SOI) wafer by solid-source molecular beam epitaxy (SS-MBE), and the PIN diode is fabricated by selective ion implantation around the PhC cavity. Under an injected current larger than 0.5 mA, strong resonant electroluminescence (EL) around 1.3-1.5 μm wavelength corresponding to the PhC cavity modes is observed. A sharp peak with a quality factor up to 260 is obtained in the EL spectrum. These results show a possible way to realize practical silicon-based light emitting devices.