NOVELTY - A hydrogen generating apparatus is pre-processed by denaturation process of carbon monoxide in process gas produced by modification part (11) according to carbon monoxide conversion catalyst at carbon dioxide, reduction process in which 1st gas containing reducing agent which reduces carbon monoxide conversion catalyst is introduced into carbon monoxide conversion part (12) from 1st gas introduction part, and discharging residual gas by which greater than or equal to 1 part of reducing agent in the mixed 3rd gas for reduction process is consumed from residual gas discharge part.    USE - Pre-processing of hydrogen generating apparatus (claimed).    ADVANTAGE - The pre-processing time of the hydrogen generating apparatus can be shortened.    DETAILED DESCRIPTION - A hydrogen generating apparatus is pre-processed by denaturation process of carbon monoxide in process gas produced by modification part (11) according to carbon monoxide conversion catalyst at carbon dioxide, reduction process in which 1st gas containing reducing agent which reduces carbon monoxide conversion catalyst is introduced into carbon monoxide conversion part (12) from 1st gas introduction part, reduction process in which 2nd gas mixed with residual gas by which 1 part of reducing agent in 1st gas for reduction process is consumed is introduced from 2nd gas introducing part, and discharging residual gas by which greater than or equal to 1 part of reducing agent in the mixed 3rd gas for reduction process is consumed from residual gas discharge part. An INDEPENDENT CLAIM is included for a hydrogen generating apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the hydrogen generating apparatus (fuel treating apparatus) of the fuel cell power generation system. (Drawing includes non-English language text).    Raw fuel gas reforming inlet part (10)    Modification part (11)    Carbon monoxide conversion part (12)    Carbon monoxide removal part (13)    Fuel reformed gas exit part (14)