The purpose of this study was to assess physical activity levels during cycling at a given spontaneously chosen speed on a 3.2 km of test road with a flat road, and 3% or 6% gradient slope roads, using different support settings; no support (assist-OFF) and support (assist-ON), with an electrically power-assisted bicycle. Twenty healthy women volunteered for this study. The physical activity levels estimated by %HRR on the slope roads for assist-OFF reached the recommended level for health promotion. However, those for assist-ON, which were 30% lower than those for assist-OFF, did not reach the recommended level. The net energy consumption while cycling on the test road for assist-ON was 30% lower than that for assist-OFF. From the standpoint of health science, we need to decrease the power-assist level or switch off the power according to the gradient of the road.