The interference effect caused by a task-irrelevant distracter could be decreased simply by adding a flanker in the Stroop task. To observe the time course during the cognitive process considering from early perception to cognitive conflict while performing a Stroop task which an additional diluter is added to, we used event-related potentials (ERPs). Subjects were asked to make categorization responses as fast as possible, concerning the occupation of a presented name (politician, pop star, actor, or athlete) while ignoring a distracter located beside the name. The distracter could be either a face of an individual from the same occupational category of the named person (congruent condition) or a face of a person from another occupational category (incongruent condition). A famous face distracter was presented (1) alone, (2) with a neutral anonymous face, or (3) with a fearful anonymous face. In the result of the behavioral data, the Stroop interference was diluted when the anonymous face diluter was accompanied with the name and the famous face distracter. However, the difference of the Stroop interferences between in the fearful face and in the neutral face diluter conditions was not significant. In the ERP results, N170 showed more negativity when another face was added, implying that the perceptual load increased when two faces were presented. And a similar effect was observed at the fronto-central area between 200 and 350 ms post-stimuli. However, there is no significant difference between the emotional and the neutral diluter conditions. This result can be considered as an influence of the increased perceptual load forwarded from the perceptual areas to the region of cognitive control. The amplitude of N400 between 400 to 600 ms post-stimuli which is related to cognitive conflict in the Stroop task showed significant difference between the congruency conditions but, not affected by the diluter condition. These results consistently suggest that perceptual load which could be inferred by different N170 among diluter conditions, is an important variable to originate the Stroop dilution effect.