Poly(N-isopropylacrylamide) (poly(NIPAM)) film spread at the air-water interface from its aqueous solution has been investigated by surface pressure and ellipsometric measurements at two temperatures (16.0 and 31.3-degrees-C). The surface pressure steeply increased at low real spread concentration of poly(NIPAM), and it more gradually attained a plateau one at high temperature. The plateau surface pressure at 16.0-degrees-C was lower than that at 31.3-degrees-C. The amount of polymer adsorbed at the air-water interface was determined by ellipsometry, and its plateau adsorbed amount at 31.3-degrees-C was twice as large as that at 16.0-degrees-C, whereas the thickness of the adsorbed layer at 16.0-degrees-C was larger than that at 31.3-degrees-C. Such an adsorption behavior at the air-water interface was strongly related to the transition of poly(NIPAM) from a hydrophilic to a hydrophobic structure in bulk solution. Moreover, it was found that some portions of the spread polymer were desorbed from the interface and the magnitude of the adsorbed amount was similar to that on the silica surfaces.