Current measurements made with a Doppler Current Profiler were taken along cross sections in the Obatake Seto Strait, a small strait in the western part of the Seto Inland Sea. The energy loss between two cross sections of the strait was estimated using the control volume analysis of the stationary one-dimensional energy equation. The large energy loss observed in the strait cannot be explained in terms of general bottom friction in the coastal region. The loss is attributed to the form loss, which is accompanied by internal turbulence and vortices generated by the specific topography of the strait, in addition to the loss by friction. This is supported by the fact that the energy loss in the strait differs, depending upon the current direction.