Many studies have used the P300 as an index for cognitive processing and neurological/psychiatric disorders. Here, we combined the source separation and source localization methods to investigate the cortical origins of the P300 elicited in a facial attractiveness judgment task. For each participant, we applied second-order blind identification (SOBI) to continuous EEG data to decompose the mixture of brain signals and noise. We then used the equivalent current dipole (ECD) models to estimate the centrality of the SOBI-recovered P300. We found that the ECD models, consisting of dipoles in the frontal and posterior association cortices, account for 96.5 ± 0.5% of variance in the scalp projection of the component. Given that the recovered dipole activities in different brain regions share the same time course with different weights, we conclude that the P300 originates from synchronized activity between anterior and posterior parts of the brain.