Farmland abandonment contributes to agroecosystem degradation and food crises. Sustainable farmland use requires a well-designed agri-environmental policy to provide farmers with incentives, including agroecosystem services apart from food production. One of these is recreation. Here, we focus on a Japanese terraced paddy land. We assessed seasonal changes in the value of recreational ecosystem services by integrating mobile phone big data of on-site visitors, collected between 2018 and 2020, into a valuation method. The application of mobile data enables the precise and consistent analysis of non-market agroecosystem services. The recreational value of the paddy land varied with season but overall was high. Sustainable farmland use provides social benefits, and we support the validity of agri-environmental policies that relate to economic incentives for agroecosystem conservation. However, the results show that the incentives provided by the public/government may be insufficient in comparison to this recreational value. Our findings provide information regarding the appropriate amount of economic support required to achieve sustainable agricultural land use in this setting.