Experimental results on micro-hollow cathode discharge are presented. First, breakdown voltages in air glow discharge and current-voltage characteristics are examined with a hollow cathode, 0.8mm in diameter and 3mm depth separated by ceramic insulator of 1mm thickness. Then electron temperatures and rotational temperatures in negative glow plasma in hollow cathode are measured by optical emission spectroscopy, intensity ratio of hydrogen line-spectra and spectral intensity distribution of nitrogen first negative band respectively. Electron temperatures measured decreased from 2eV to 0.5eV, increasing discharge current from 10mA to 120mA at about a few kilo-Pa. And gas temperature, corresponding to rotational temperature increased from 0.03eV to 0.14eV with the same increase of current. But with collisional-radiative model, calculated electron temperatures, from 5eV to 1eV for the same current decrease, are higher than experimentally obtained result. This difference means that negative glow plasma does not attain in thermo-dynamical equilibrium.