The objecitve of this study was to investigate whether social anxiety could facilitate the discrimination between smiles and sneers by applying point of subjective equality (PSE) and signal detection theory (SDT). A total of 85 undergraduate and graduate participants completed self-report measures about social anxiety and depression symptoms. Thereafter, they participated in emotion recognition tasks through a computer-based experiment. Facial emotion stimuli were composed of smiling and sneering faces at different ratios (2:8, 3:7, 4:6, 5:5, 6:4, 7:3, and 8:2). Participants in each trial performed two alternative forced choice tasks where they had to categorized one facial stimulus as “smile” or “sneer”. We estimated PSEs by fitting the curve into the cumulative normal distribution function. By applying signal detection theory, we also examined sensitivity (d’) and response criterion (c) for each expression. Results indicated that levels of participants’ social anxiety were positively correlated with their PSEs but negatively correlated with response criterion. These results suggest that individuals with higher social anxiety are more likely judge smiles as sneers. However, these relations were not significant when depression levels were controlled, suggesting that such tendency might be a trait shared with depression rather than a unique characteristic of social anxiety.