NOVELTY - A fuel cell in-plane state estimating system comprises a membrane electrode assembly of a fuel cell having an anode and a cathode to which reactive gases are respectively supplied to generate power; power generation characteristic storing mechanism; consumption production characteristic storing mechanism; inlet environment deciding mechanism; small region defining mechanism; power generation amount calculating mechanism; consumption production amount calculating mechanism; and power generation environment updating mechanism.    USE - Fuel cell in-plane state estimating system.    ADVANTAGE - The fuel cell in-plane state estimating system easily and accurately estimates current distribution in a plane of each membrane electrode assemblies constituting a fuel cell.    DETAILED DESCRIPTION - A fuel cell in-plane state estimating system comprises a membrane electrode assembly of a fuel cell having an anode and a cathode to which reactive gases are respectively supplied to generate power; power generation characteristic storing mechanism; consumption production characteristic storing mechanism; inlet environment deciding mechanism; small region defining mechanism; power generation amount calculating mechanism; consumption production amount calculating mechanism; and power generation environment updating mechanism. The power generation characteristic storing mechanism stores a power generation characteristic defining a relationship between a power generation amount and a power generation environment of the membrane electrode assembly. The consumption production characteristic storing mechanism stores a consumption production characteristic defining a relationship between consumption amounts of the reactive gases in the membrane electrode assembly and the power generation amount, and a relationship between a production amount of water in the membrane electrode assembly and the power generation amount. The inlet environment deciding mechanism decides power generation environments at inlets of the reactive gases. The small region defining mechanism virtually divides the membrane electrode assembly into small regions arranged along flow of the reactive gases. The power generation amount calculating mechanism calculates a power generation amount of a first small region as one of the small regions on a basis of a power generation environment of another small region upstream of the first small region with respect to flow of the reactive gases according to the power generation characteristic. The consumption production amount calculating mechanism calculates consumption amounts of the reactive gases and a production amount of water in the first small region on a basis of the power generation amount of the first small region according to the consumption production characteristic. The power generation environment updating mechanism reflects consumption amounts of the reactive gases and a production amount of water in the other small region on the power generation environment of the other small region to calculate a power generation environment of the first small region.    DESCRIPTION OF DRAWING(S) - The drawing is a plan view of a diagram of a procedure in which the system predicts a power generation environment of a number of regions on the basis of a power generation environment of the regions minus one.    Calculating cathode relative humidity (124)    Calculating cathode pressure (125)    Determining oxygen concentration (126)    Calculating anode relative humidity (130)    Calculating anode pressure (131)    Calculating oxygen consumption (138)    Determining amount of oxygen flowing out (140)    Determining amount of hydrogen flowing out (148)