The purpose of this paper is to quantitatively measure the effect of the CPTPP on Japan's exports to member countries, and to find out various factors affecting Japan's exports. In this study, we adopt the spatial Durbin gravity model to consider the spatial dependency and spillover effects of trade flows between Japan and CPTPP member countries during the period from 2017 to 2021. While the CPTPP did not directly increase Japan's exports, it had an indirect spillover effect due to increased trade among other CPTPP member countries, which decreased Japan's exports. The factors that have a more direct impact on Japan's exports to CPTPP member countries are currently GDP of both countries, distance between countries, and the exchange rate. In particular, the direct effect of the exchange rate is most significant, as a depreciation of the Japanese yen enhances the price competitiveness of Japanese products, resulting in increased exports.