Introduction: Bipolar disorder (BD) is an emotional disorder characterized by emotional instability. This study aims to investigate whether emotional disorders affect the cortical processing that regulates emotional stimuli. Methods: This study uses a passive viewing paradigm to compare event-related potentials (ERPs) of 21 subjects with bipolar disorder (BD), 25 subjects with schizophrenia (SZ), and 25 normal subjects (HC). Results: In the frontal and parietal areas (1) the late positive potential (LPP) amplitude of BD was greater than that of SZ and HC, and there was no difference in terms of peak latency. (2) In the occipital area, the amplitude and latency of P300 of SZ and BD were significantly larger than HC, but there was no difference between SZ and BD. (3) The behavioral results demonstrated that BDs’ valence rating on both positive and negative stimuli were significantly higher than those of HC and SZ when viewing face images, while BDs’ arousal scores for positive stimuli were significantly lower than HC and SZ. BDs’ arousal score for negative stimuli was significantly higher than those of HC and SZ. When viewing non-face pictures, BDs’ positive valence rating on negative stimuli and arousal scores for positive stimuli were significantly higher than those of HC and SZ. Conclusion: Bipolar patients have complete early emotional recognition, and their emotional abnormalities exist in the late evaluation of emotional stimuli, mainly occurring in the frontal and parietal areas.