Abstract：Previous studies on social equality have exclusively focus on the effect of outcome equality during outcome evaluation. However, the effect of opportunity equality during outcome evaluation remains unknown. The aim of the present study was to explore the temporal dynamics of opportunity equality during outcome evaluations, by using ERPs technique. The results showed disadvantageous opportunity unequal condition evoked a larger feedback negativity (FRN) amplitude than the other two conditions, reflecting disadvantageous opportunity unequal was a major concern of people. The results showed disadvantageous opportunity unequal and advantageous opportunity unequal conditions elicited greater P300 amplitudes than opportunity equal condition when participants witnessed a win outcome, while the difference among three conditions was not found when participants witnessed a loss outcome. These findings indicated opportunity-equality degree could modulate outcome evaluation, shown by FRN and P300 amplitudes.