In recent years, many documents are created as an electronic one and are distributed. Although those costs were reduced remarkably, the copy of a document could also be created easily. Spreading of plagiarism or violation of copyright is the big issue which controls production of a valuable document. Therefore, the system which detects plagiarism is very important. Many plagiarism detection systems have aimed to detect a document chiefly similar to query. However, it is not easy to detect a partially similar document. When the document with the possibility to plagiarize or to be plagiarized is not given, the detection of a similar document by mutual comparisons of all documents is more difficult. We propose the method that detects partial copies from documents without query. Some partial copies were detected from test documents.