Previous studies have reported that observation pressure and outcome pressure impact working memory, but have not investigated whether they exert different effects on working memory. The neuronal activity in some brain areas encodes task-related information corresponding to working memory across delay periods. Therefore, changes in working memory under pressure can be further verified by exploring neuronal activity changes in brain areas under pressure. In this study, we used an N-back task and event-related potentials to explore whether the two types of pressure exert different effects on working memory. The electrophysiological results revealed that observation pressure-induced P1, P2 and late positive component amplitudes are significantly larger than corresponding outcome pressure-induced amplitudes, and the P3 amplitude induced by low-load working memory is significantly larger than that in the high-load condition. A possible explanation is that observation pressure increases attention focus, whereas outcome pressure increases attention dispersion, and a greater memory load results in more information that must be maintained and updated in working memory. These findings indicate that observation pressure and outcome pressure exert different effects on working memory.