Method, apparatus and storage medium for managing contents and adaptive contents playback method using the same

A content management method includes transmitting content from a content provider device to a client device over a predetermined network; and adding additional information comprising original content location information of the content transmitted to the client device and elapsed playing time information of the content. A content management device includes a communication module which transmits content to, receives content from, or transmits content to and receives content from a device connected over a predetermined network; an additional information edit processing unit which generates additional information comprising original content location information of the content transmitted by the communication module and elapsed playing time information of the content, and inserts the additional information into the transmitted content; and a storage unit which stores the content into which the additional information has been inserted.