The present invention discloses a patent retrieving apparatus. The apparatus comprises: a client computer, an extended database, a retrieving module and a display module. An output end of the client computer is connected to an input end of the retrieving module; an output end of the retrieving module is connected to an input end of the extended database and an input end of the display module separately; and the retrieving module comprises a retrieving type selection module, a retrieving input module and a retrieving pairing module, wherein the retrieving type selection module comprises a simple retrieving selection module, a high-level retrieving selection module and an expression retrieving selection module, and the retrieving input module comprises a simple retrieving input module, a high-level retrieving input module and an expression retrieving input module. The patent retrieving apparatus disclosed by the present invention is simple in operation, short in patent search time and high in efficiency; an omission ratio can be reduced by automatic expansion of keyword explanation, so that work efficiency of retrieval staff is improved; and retrieving precision can be adjusted arbitrarily in the retrieving process, so that the retrieving process is more convenient and accurate.