BACKGROUND A large amount of healthcare data has been produced and accumulated in recent years: big data derived from hospital records, patient medical records, medical examinations, and other sources. These data require proper management and analysis to derive meaningful results to improve healthcare. For proper management, the data must be integrated, secured, and made interoperable between individuals, hospitals, and companies, while protecting patient privacy. OBJECTIVE The purpose of this research was to create a healthcare data marketplace using a blockchain-based business-to-consumer model that ensured the integration, security, and interoperability of healthcare data between individuals, hospitals, companies, and marketplaces. This marketplace should enable direct transactions of healthcare data between companies that need individual healthcare data and individuals who own the data. METHODS To investigate the essential elements of a healthcare data marketplace, we considered two aspects: technology and service. A healthcare data marketplace was created using MySQL 8.0, JavaScript library, and Node.js software. The marketplace system featured security of data, access for companies and individuals, and a data transaction monitor. Furthermore, anonymization and standardization of data were implemented. A web-based application was developed for implementation of the marketplace system, along with a mobile application system for use by individuals. Finally, we evaluated the performance of the data marketplace system in three scenarios: male and obese (BMI ≥30 kg/m2); male aged ≥40 years with abnormal liver function tests (aspartate aminotransferase ≥40 units/L and alanine aminotransferase ≥40 units/L); and female aged ≥60 years with high blood pressure (systolic pressure ≥130 mmHg and diastolic pressure ≥90 mmHg). RESULTS A web-based application was developed to implement the healthcare data marketplace; a mobile application was also developed for individuals who provide their healthcare data. The performance of the data marketplace was evaluated through the three scenarios by calculating the time taken for completion of each scenario. A data query was executed fully within about 1–2 s; approximately 9.5 healthcare data queries were processed per minute in each scenario. CONCLUSIONS We successfully created a prototype of a healthcare data marketplace that ensured the integrity and security of data through its honest broker design.