We describe a system for sharing distributed XML data among organizations using customizable schema. In our system, each organization can customize common DTD (Document Type Definition) within the bound of rule to create its own DTD, which is called customized DTD. And then it can describe information with tags according to the customized DTD. Basically, the upper structure of shared XML data is common. Proposed system consists of a management server, data providing servers, and application servers. They communicate with each other through web services technology. Customized DTDs are managed centrally by the management server. The server also examines whether they conform to the rule of customization. As a result of prototype system using welfare information, we found that our system was effective for sharing information among organizations of which each works freely in the same field.