Previous studies have demonstrated the influences of facial emotionality on attentional and perceptual processing when socially anxious individuals perceive threatening information from facial expressions. However, it remains unclear whether and how positive expressions may also affect the attention and perception of socially anxious individuals. This event-related potential (ERP) study addresses this issue and examines the temporal dynamics of electrophysiological responses to negative and positive faces in individuals with high (HSA; n = 56) or low (LSA; n = 47) social anxiety in a dot-probe task. Four face pairs (neutral-neutral, angry-neutral, happy-neutral, and angry-happy) were presented to probe the influences of positive and negative emotionality. The behavioural results showed a greater negative bias in reaction times for the LSA group than the HSA group when angry-happy face pairs were presented. Our ERP results showed an enhanced N170 effect for the LSA group in comparison to the HSA group when emotional faces were presented in angry-neutral, happy-neutral, and angry-happy face pairs. Moreover, greater N2pc effects on emotional faces were found in the HSA group when angry-neutral and happy-neutral face pairs were presented. However, this was not true for the LSA group. No N2pc effect was found when both positive and negative faces were presented simultaneously. We did not find any significant P1 effect. Together, our results showed that facial emotionality influenced facial processing and attention bias in relation to social anxiety. Socially anxious individuals perceived less emotional facial information and had attention biases towards both negative and positive faces.