Brewster angle microscopic (BAM) study was successfully achieved for photoresponsive monolayers composed of poly(vinyl alcohol) derivatives bearing an azobenzene (At) side chain. BAM observation revealed clear differences in the morphological and rheological properties between the trans- and cis-isomerized monolayers. The deformation process was also monitored under UV irradiation, which correspondingly visualized the magnitude of expansion stemmed from the difference in the methylene spacer length of the amphiphilic Az polymer.