A right information management method for managing a right information of contents retained in a storage medium comprising an authenticated memory region accessible after a mutual authentication is obtained relative to a contents processing device and an ordinary memory region accessible without obtaining the mutual authentication, comprising a step of reading an encrypted right information retained in the authenticated memory region, a step of decoding the read encrypted right information and retrieving a plaintext right information, and a step of retaining the plaintext right information in the ordinary memory region. According to the right information management method, a user can be notified of the contents and the right information of the contents managed in the storage medium in a speedy manner via the contents processing device.