Given resource constraints, climate change adaptation policies require fine-grained monetary valuation of vulnerable ecosystem services at the national scale to consider policy priority setting. However, prevailing evaluations have been spatially and temporally limited due to technical limitations. This study adopts a traditional economic valuation approach using mobile phone network data to reveal the current nationwide human welfare of coastal recreation at Japanese beaches in summer and winter, and to project the change in value based on four climate change scenarios (Representative Concentration Pathway; RCP2.6; RCP4.5; RCP6.0; and RCP8.5). The approach used in this study identifies 274 nationwide current coastal recreational values, which ranged between 4,865 JPY and 36,136,364 JPY in summer, and 1,684 JPY and 19,842,105 JPY in winter. However, the projected economic values drop to less than a quarter of the current values under the RCP2.6 scenario and become smaller as the climate scenarios worsen to reach less than one-tenth for the RCP8.5 in both seasons. On a national scale, the value loss rates are substantially larger than the physical loss rate under the four climate change scenarios, which implies that only the existing physical evaluations are insufficient to support policymaking. Furthermore, the geographical insights demonstrate regional differences in recreational values: most southern beaches with larger current values would disappear while the current small values of the northern beaches would remain relatively the same. These changes imply that the ranks of the beaches based on economic values enable policymakers to discuss management priorities under climate change.