The invention provides a content processing technique which enables to prevent a reading person from easily guessing the fact of hiding and hidden information, and to obtain a content having natural information close to information of its original content before hiding. A content processor includes a search means which searches contents having information similar to a part excluding a part to be hidden in the original content, an arithmetic means which calculates non-similarity which shows the degree of non-similarity of each content obtained by the search means to the part to be hidden of the contend, and a selection means which selects the content which is the least similar to the part to be hidden out of the contents searched by the search means.