The concentrator solar cell system significantly reduces the number or area of expensive cells and then contributes to the curtailment of the total investment. It is acknowledged in US and European countries that the well-designed concentrator PV (PhotoVoltaics) cost reaches down to the 6 - 8 cents/kWh range. In this research, the yearly photon number was calculated for a tracking concentrator PV in 26 principle sunshine sites in Japan on a new model. This model was also applied to the quantitative analysis of the spectrum mismatching loss inherent in III-V multi-junction solar cells. Authors expect that the generation cost will be 20 yen/kWh even in Japan if the PV costs modestly.