Individuals engage in upward or downward comparisons with superiors or inferiors, respectively. Social comparison is associated with social anxiety. Utilizing event-related potentials, we investigated how individuals with high social anxiety (HSA) and low social anxiety (LSA) evaluate self- versus other-outcomes in upward and downward comparison contexts. We found significant valence effects of self- or other-outcomes on feedback-related negativity (FRN) and P300 for both groups, with loss inducing larger FRN and smaller P300 than gain. In the early stage, the valence effect of other-outcomes was significant when LSA participants gained money, but not when they lost money, revealing a social comparison effect on FRN. Conversely, this valence effect was significant whether HSA participants gained or lost money. At the late stage, the valence effect of other-outcomes was significant when HSA or LSA participants gained money but not when they lost, revealing social comparison effects on the P300. Notably, only the social comparison effect in the LSA group was further moderated by comparison direction. These findings suggest that LSA participants engaged in social comparison throughout all evaluation stages, whereas HSA participants started at the late stage. Moreover, LSA participants were more sensitive to different comparison directions in the late stage.