NOVELTY - A fuel cell system comprises suppressing unit that sets suppression state where after termination of normal power generation of fuel cell, an introduction of fuel gas to anode-side passage and oxidation gas to cathode-side passage are suppressed, and emission of fuel gas from anode-side passage and emission of oxidation gas from cathode-side passage to outside of each passages are suppressed as compared during normal power generation; and abnormality detecting unit that detects abnormality of system on basis of voltage detected by voltage detecting unit or variation in detected voltage.    USE - A fuel cell system.    ADVANTAGE - The system eliminates partial oxidation reaction in the cathode thus suppressing degradation of a fuel cell.    DETAILED DESCRIPTION - A fuel cell system comprises:    (1) a fuel cell including fuel-cell cell(s) having an anode, a cathode and an electrolyte membrane;    (2) an anode-side passage that supplies and exhausts fuel gas to and from the anode of the fuel-cell cell(s);    (3) a cathode-side passage that supplies and exhausts oxidation gas to and from the cathode of the fuel-cell cell(s);    (4) a voltage detecting unit that detects a voltage of the fuel cell;    (5) a suppressing unit that sets a suppression state where after normal power generation of the fuel cell is terminated, an introduction of the fuel gas to the anode-side passage and introduction of the oxidation gas to the cathode-side passage are suppressed as compared with those during the normal power generation, and emission of the fuel gas from the anode-side passage to an outside of the anode-side passage and emission of the oxidation gas from the cathode-side passage to an outside of the cathode-side passage are suppressed as compared with those during the normal power generation; and    (6) an abnormality detecting unit that, after the suppression state is set by the suppressing unit, detects abnormality of the fuel cell system on the basis of the voltage detected by the voltage detecting unit or a variation in the detected voltage.    An INDEPENDENT CLAIM is included for abnormality detection of a fuel cell system    DESCRIPTION OF DRAWING(S) - The drawing is a flowchart of an abnormality detecting process executed by the fuel cell system.    Detect amount of hydrogen (S10)    Determine that suppressing unit is abnormal (S50)    Turn on abnormality detecting flag (S60)    Notify abnormality (S70)    Determine that suppressing unit is normal (S80)