Recently, the manufacture and distribution of adulterated gasoline mixed with pure commercial gasoline and adulterants has become a global problem. However, there is still a lack of a simple way to detect it immediately on-the-spot. In this study, we propose highly reflective one-dimensional photonic crystals (1D PC) as a simple, on-the-spot detection method for adulterated gasoline with the naked-eye. First, a photo cross-linked polymer–TiO₂ hybrid material (Ti70) with a high refractive index and P(MA-co-BPA) with a low refractive index were synthesized and analyzed. After that, they were used to fabricate a total of 11 layers of highly reflective Ti70/P(MA-co-BPA) 1D PC. The fabricated Ti70/P(MA-co-BPA) 1D PC exhibited purple in pristine and no color change was observed when immersed in pure commercial gasoline. On the other hand, when immersed in methanol, xylene, toluene, and benzene, the colors of Ti70/P(MA-co-BPA) 1D PCs changed rapidly to strong blue, blue, yellow-green, and orange, respectively. In addition, Ti70/P(MA-co-BPA) 1D PC showed color change within a short time (~10 s) even in binary or ternary solvent mixtures(gasoline-toluene, gasoline-methanol, gasoline-toluene-methanol). Moreover, the excellent reusability of Ti70/P(MA-co-BPA) 1D PC was verified through 10 repetitions of swelling-deswelling tests. Through these results, it was confirmed that the novel Ti70/P(MA-co-BPA) 1D PC can be successfully applied to the colorimetric on-the-spot detection of adulterated gasoline.