The purpose of this study is to explicate the primary factor regarding the confluence of two traffic flows in staircase. Using an emergency staircase of standardised size, dividing about 150 subjects into two groups. We made these two groups flow into staircase from diferent floor like an evacuation exercise. As a result of this experiment, the following findings have been obtained. (1) These experiments show a tendency that flow from corridor become predominant consequently. Throughout during the period of constant flow, "the ratio of flow-rate" (flow-rate from corridor / total flow-rate) is about 60 %. Further we shoud like to add that "flow-rate" is defined by the number of person that flow to confluence area per second-meter. (2) Flow-rate of each group moves 10-15 seconds cycle. In this experiment, the influence of habituation cannot be disregarded owing to the same subjects behave same trial for five times continuously.