The percept of illusory contours provides a unique window for exploring the brain mechanisms underlying visual perception. Previous electrophysiological single-cell recordings demonstrated a subgroup of cells in macaque V1 and V2 that signal the presence of illusory contours, whereas recent human brain imaging studies revealed higher-order visual cortices playing a central role in illusory figure processing. It seems that the processing of illusory contours/figures may engage multiple cortical interactions within the hierarchically organized ventral visual pathway in primates. It is not yet known in which brain area(s) after V1 and V2 in macaque illusory contours are represented in the same manner as real contours at both the population and single-cell level. Here, by combining intrinsic optical imaging in anesthetized rhesus macaques with single-cell recordings in awake ones, we report a complete overlap of orientation domains in visual cortical area V4 for processing real and illusory contours, whereas the orientation domains mapped in early visual areas V1 and V2 mainly encode the local physical stimulus features inducing the subjective perception of global illusory contours. Our results suggest that V4 is a key cortical locus where real and illusory contours are encoded equivalently and for form-cue invariant representation of boundary orientation in general.