A method and apparatus for processing digital rights managements (DRM) contents having advertisement (AD) contents attached thereto in a DRM system are disclosed. When DRM contents including AD contents are selected by a DRM device, a rights issuer (RI) receives the AD contents and the DRM contents from a contents issuer (CI), generates a multipart contents format file, and downloads it to the DRM device. Then, the DRM device decodes the downloaded multipart contents format file to check whether the multipart contents format file includes AD contents-attached DRM contents, and if so, the DRM device reproduces the AD contents to use the DRM contents free of cost. Thus, the DRM contents can be provided to a user by using the AD contents without causing a burden of a charge.