A magneto-optical microscope magnetometer (MOMM) has been developed to simultaneously measure 2-dimensional array hysteresis loops of each local area of $320 imes320-nm^2$ spots on ferromagnetic films, in addition to grabbing time-resolved domain evolution patterns. Using the system, spatial distribution of local coercivity can be quantitatively generated and then, compared directly with domain patterns grabbed at precisely the same position of a sample. It is clearly demonstrated that local coercivity distribution governs domain reversal behavior via a thermally activated relaxation process.