The problem to be solved is to allow anyone other than the contents license owner to acquire a right usage opportunity of contents while the fraud in the contents can be detected. To solve this problem, a contents ID, distribution media information specifying the distribution media of the contents, and identification information containing distribution period information specifying the distribution period of the contents are attached to the contents body When a contents acceptance module 140 receives the contents data, an acquisition pattern recognition unit 142 recognizes the acquisition pattern information of the contents data. A identification information extraction module 154 of a contents validity determination module 150 extracts identification information from the contents data. A validity determination unit 153 compares the condition specified by this identification information with the contents acquisition media and the acquisition period indicated by the acquisition pattern information and if the acquisition pattern information satisfies the condition specified by the identification information, the contents data is stored in the contents-for-distribution file 126. Additionally, if the contents are determined to be illegal a deletion request is sent to the requestor.