The crossed beam chemiluminescence of O(3P)+NO→NO2+hv elementary reaction has been observed. The ground state oxygen atoms are produced by a microwave discharge in O2. Continuous spectra in the 4000-9666A region have been obtained. Dependence of the emission intensities on the NO flux is linear. Assuming the reaction obeys adiabatic correlation, the "chemiluminesecence should be due mainly to the transition 2B1→2A1 of NO2 molecules. This experimental result is in agreement with the theoretical calculation by Grangi et al..