We propose optimum arrangement of taxi drivers’ working hours. In Japan, income of taxi vehicle is decreasing about 11 thousand yen in the past 15 years. Then some taxi companies are investing to gain more customers. But there are many small taxi companies that are difficult to invest with much money. Therefore we have been researching the other method to gain more customers by little investment for small companies. In this paper, we analyze present situation of the Taxi Company which we research, research optimum arrangement of taxi drivers’ working hours so as to increase sales amount using mathematical model, and verify validity of our method with numerical calculation.