Abstract: A paper processing apparatus including a paper supplier for supplying papers one by one. A checker reads the papers supplied by the paper supplier to check at least whether the papers are complete or dirty papers. A transferrer transfers the papers checked by the checker. A collector collects papers checked as complete papers by the checker from among the papers transferred by the transferrer. A brancher branches papers checked as dirty papers by the checker from among the papers transferred by the transferrer. A discarder discards dirty papers branched by the brancher. A detector detects an abnormality of the transferrer and the discarder. A controller controls the brancher before the checker determines the checking result such that dirty papers are collected in the collector when an abnormality is detected in at least either the transferrer or the discarder by the detector.