We theoretically and experimentally demonstrate low loss branches in a Si photonic wire waveguide. Approximate calculation by the two-dimensional finite-difference time-domain (2-D FDTD) method and detailed design by the 3-D FDTD method indicate that low excess loss less than 0.2 dB is expected for a µm-size bend-waveguide-type branch at a wavelength of 1.55 µm. This branch is fabricated in a silicon-on-insulator substrate and the loss is evaluated to be 0.3 dB. This value is small enough to construct a very compact branching circuit.