Tungsten trioxide (WO3) is a typical electrochromic material that exhibits reversible optical property changes depending on the applied voltage. Previously, studies for its application in smart windows and various technologies have been made. However, improvements to the WO3-specific low color change rate are needed. The above problem can be solved by fabricating a color change layer with a large specific surface area through physical/chemical modification of the WO3 layer and structural control for smooth electrolyte injection. In this study, three dimensional porous WO3 nanostructures were prepared using polystyrene nanospheres. Inverse opal structured WO3 thin films with high porosity showed excellent electrochromic properties. The change in transmittance was 86% at a wavelength of 700 nm; the response time was 5.55 s; and the coloration efficiency was calculated at 154.94 cm(2)/C. The response time was about 3 times faster and the coloration efficiency was about 2 times higher than that of the flat thin film. As a result, the WO3 thin film with an inverted opal structure exhibited excellent electro reversibility and enhanced properties.