This paper proposes an encryption scheme maintaining hierarchy of JPEG 2000 codestreams for flexible access control. JPEG 2000 generates hierarchical codestreams and has flexible scalability, such as, SNR, space, or color components. In a proposed method, only one managed key (master key) exists, and for a user permitted to access a reserved image quality, only one key generated by the master key is delivered. Also, a different key generated by the master key is delivered for a user permitted to access a different quality. The proposed access control method is available for all kinds of JPEG 2000 scalability. On the other hand, some conventional methods need several keys to control image quality. Another conventional method is not suitable for JPEG 2000 scalability.