The step-flow mode growth of an In-polar InN epilayer on a GaN template was achieved by molecular beam epitaxy. A uniform terrace structure was observed with a step height of one monolayer. The surface rms roughness was less than 1 nm over a 10×10 µm2 area. To obtain the step-flow mode growth, it was preferable to use a slightly In-rich growth condition in the In-polarity growth regime, a GaN template of low dislocation density, and a high epitaxial temperature. A typical electron concentration of bulk InN was 5–6×1017 cm-3 with a Hall mobility of 1400 cm2/(V s).