Objective: Personal Health Record (PHR) application would provide a way for patients to access their clinical data. When PHR connects with multiple Electronic Health Records (EHRs), doctors and patients can share a large amount of patient data from the EHR (for example, medication list, diagnoses, allergies), as well as personal daily records from PHR (for example, blood pressure and exercise). However, no standard interoperability between EHRs and PHR has been established. The recently introduced Health Level 7 (HL7) Fast Health Interoperability Resource (FHIR) is expected to fix this problem. In Japan, Standardized Structured Medical Information eXchange version 2 (SS-MIX2) is commonly used for EHRs and the Health Information Exchange (HIE). Therefore, the aim of this study was to convert clinical data in SS-MIX2 into HL7 FHIR data format and to develop a PHR application showing FHIR data. Methods: The SS-MIX2 data used in this study were obtained from SS-MIX2 storage at Tohoku University Hospital. We converted SS-MIX2 data into FHIR based on the mapping method provided by IRIS Health (InterSystems). After that, the FHIR data is stored via the REST API in the FHIR repository server using the STU3 standard. In addition, we used Swift4.0, based on Xcode 11, to build an IOS application. The application utilizes the FHIR REST API to retrieve patient data from the FHIR server. Results: We developed an application that can retrieve clinical data from the FHIR server to display patients’ clinical information. In addition, we converted patients’ basic information, diagnostic reports, prescriptions, diseases, and injection data from SS-MIX2 to FHIR and used them as a dataset in our application to present a use case. Conclusion: Our work demonstrates that it is feasible to convert SS-MIX2 data into FHIR and present them with our PHR application.