The present invention solves a problem of conventional tissue treating apparatuses: liquid chemicals which have been used given times and have become useless in a tissue specimen infiltration treatment and a cleaning liquid which has been used given times and has decreased in cleaning ability are required to be separately discarded/replaces. The tissue treating apparatus (10), which supplies given liquid chemicals to and discharges the same from a processing chamber (12) containing a tissue specimen so as to perform the tissue specimen infiltration treatment, comprises: liquid-chemical reservoirs (14, 16) for storing the liquid chemicals to be used in the infiltration treatment; cleaning-liquid reservoirs (19, 21) for storing the liquid chemicals which have become useless in the tissue specimen infiltration treatment and which are usable as cleaning liquids for removing a residual liquid chemical remaining in the processing chamber (12); and cleaning means for supplying the liquid chemicals in the cleaning-liquid reservoirs (19, 21) to and discharging the same from the processing chamber (12) so as to clean the inside of the processing chamber (12).