We propose improvement method of service productivity for Taxi Company of rearranging taxi drivers working hours. There are two ways a taxi company gets customers. One is to deliver taxi for a telephone request, and the other is to get customers on street. In Japan, there are many taxi companies where the ratio of the former method is higher. Therefore we research rearrangement method of the taxi drivers working hours so as to operate many taxis with many telephone requests. We find it effective strategy to increase taxi drivers in midnight and early morning with many customers per taxi instead of decreasing taxi drivers in daytime with few customers per taxi.