Event-related brain potentials (ERPs) were used to examine the electrophysiological correlates of the visual illusion effect in the Müller–Lyer illusion tasks. The participants were presented with the context of a horizontal line with two symmetric inward-pointing arrowheads or outward-pointing arrowheads, and then, they were asked to indicate whether they perceived an increase or a decrease in the line length. The behavioral results showed that there were significant differences among the four types of tasks, which meant that participants could understand different mean illusion magnitudes. The ERP results showed that both the illusion-45 and the illusion-135 elicited a more negative ERP deflection (N180–280) than did the illusion-225 and illusion-315 between 180 and 280 ms. In addition, the strong illusion stimuli elicited a more positive ERP deflection (P280–450) than did the weak illusion stimuli between 280 and 450 ms after the onset of the stimuli. Dipole source analysis of the difference wave (illusion-135−illusion-225) indicated that one generator localized in the left lateral occipital cortex and the difference wave (illusion-45−illusion-135) indicated that one generator localized in the left lingual gyrus. Our results led us to conclude that the ERP deflection in the different illusory strength might be related to the theory of attention resource distribution or because of the inverse optics problem. Then, the early visual areas lateral occipital cortex and the lingual gyrus near to the visual cortex could contribute to integrated processing in the illusory contours and top–down control processing because of the visual experiences.