In this research, characteristics of air core rectangular spiral type inductors of ㎓ band are numerical analyzed. The basic structure of inductors is a rectangular spiral having 390${mu}{ extrm}{m}$${ imes}$390${mu}{ extrm}{m}$ size, 5.5 turns, line width of 10 ${mu}{ extrm}{m}$ and line space of 10 ${mu}{ extrm}{m}$. Frequency characteristics were simulated up to 10 ㎓. The substrate was modeled as Si, Sapphire, glass and GaAs and the conductor as Cu. The thickness of the conductor was fixed at 2. The number of turns was n.5 to make the input and output terminals to be on the opposite sides. The initial inductance of the basic inductor structure was 13.0 nH, maximum inductance 60.0 nH and resonance frequency 4.25 ㎓. As the dielectric constant of the substrate was increased, the initial inductance varied only slightly, but the resonance frequency decreased considerably. As the number of turns was varied from 1.5 to 9.5, the initial inductance was increased linearly from 2.9 nH to 15.9 nH and, then, saturated at 16.9 nH. The Q factor increased only slightly. The line width and line space of inductors were varied from 5 ${mu}{ extrm}{m}$ to 20 ${mu}{ extrm}{m}$, which resulted in the decrease of the initial and maximum inductances. But the resonance frequency was increased. Q factor displayed an increase and a decrease, respectively, when the line width and line space were increased.