Gas temperature of atmospheric pressure plasma generated in air using a micro-hollow cathode discharge device was measured by optical spectroscopy. Emission spectra of molecular nitrogen, second positive band of around 337nm, was analyzed to derive rotational temperature. Identifying rotational quantum number j=10 to 30 of R-branch, corresponding intensities were measured to estimate gas temperature of air plasma by Boltzmann plot method. Obtained temperature showed relatively high value of 1572K.