This study analyzed the financial relations between local governments and the third sector from the viewpoint of execution measures of municipalities, which are main players for regional revitalization, and from the viewpoint of the legal superintendent system to non-profit organizations. First, using the local finance survey data of the Ministry of Internal Affairs and Communications, I analyzed the execution measures of municipalities and categorized them into: direct execution, commissioned execution, and indirect execution. The results are as follows. 1) The three factors of population (i.e., the small scale of municipalities, population decline and aging) influence the municipal administration execution system and the location of the third sector. 2) In municipal executive regimes, a moderate correlation is found between the three factors of population and the decline of rates of direct execution and commissioned execution, and the rise in the rate of indirect enforcement. 3) The municipal executive manner differs in the policy field, and the substitution relationship between direct execution and commissioned execution/indirect execution is different. 4) The location of the third sector is influenced differently by the three factors of population according to their types of incorporation and objectives of activities. As a policy implication, to promote regional revitalization, building up mutually beneficial relationships between municipalities and the third sector based on the administrative transformations in the manner and third sector location characteristics caused by three population factors is an issue.