A method and apparatus for decoding a right object and a method and apparatus for sharing contents using the same, the method of sharing contents including: receiving a Digital Rights Management (DRM) agent to interpret a right object corresponding to the contents; operating the received DRM agent to generate a coding key and a decoding key to code and decode the right object, respectively; decoding the received right object by using the decoding key and extracting a contents decoding key in order to decode the content; and decoding the contents received from a predetermined device by using the contents decoding key. Therefore, coded contents can be shared even in different DRM systems, and since DRM agent may be provided as software at the time the content is shared, the DRM agent need not be originally included by a device manufacturer, thereby reducing a development cost.