In this study, we investigated the functional mechanism by which spatial attention excludes unwanted information, a consequence of attention that has been consistently demonstrated at the neuronal level, the neural population level, and the overall behavioral level. The effect of spatial attention was measured using a temporal cuing paradigm. External noise, whose spatial frequency characteristics were systematically manipulated, was added to the signal stimulus. Contrast thresholds were measured as functions of the pass-band of the external noise to reveal the spatial frequency characteristics of the perceptual template in both the attended and unattended conditions. We found that spatial attention excludes external noise uniformly across all the spatial frequencies without changing the spatial frequency selectivity of the perceptual template.