The parameters of plasma, produced by a tightly focused, Q-switched ruby laser with energy 200mJ in N$_2$ gas, are experimentally estimated by the spectroscopic method, and their gas pressure dependence is studied. The gas pressures are varied between 1 and 4 atmospheric pressure. The Stark broadening of spectral lines emitted from plasma is used in the estimation of electron densities. The typical density is about order of $10^{19}[cm^{-3}]$. The electron density of plasma is increased as the gas pressure is increased. But the tempeature dependence was decreased as the gas pressure is increased.