Abstract: A medical data management system wherein patients, doctors, medical professionals except doctors, and medical institutions are registered as members, and log in using an ID and login authentication means for each member to register and preserve medical data for effective use thereof. The system comprises a management file associated with each individual medical data, in which access authority of a member to enable the member to access the medical data is recorded; and access authority addition authentication means to enable recording additionally access authority of a member in the management file, and the access authority addition authentication means exists for each patient member.