Mechanism of destruction caused by electrostatic discharge of PN junction was examined from two viewpoints; classification of destruction mode with consideration to destructive energy density, and comparison of destruction shape. Destructive energy density of PN junction was calculated based on Speakman model, and destruction mode was classified by Wunsch-Bell plot. As a result of Wunsch-Bell plot, electric discharge which occur at low resistance, for example machine model (MM: C∙R = 200pF ∙ 0Ω), resulted in adiabatic destruction that does not involve thermal diffusion. With electric discharge at high resistance, for example human body model (HBM: C∙R = 100pF ∙ 1500Ω), excessive destruction in intermediate region that involves thermal diffusion, and depending on the device, destruction at equilibrium region were proven to be reproducible. In case of MM, (adiabatic region destruction) destruction was confirmed in a wide extent of the joint part, but in case of HBM (intermediate region destruction) destruction was confirmed near the center of the joint part. From this fact, it was found that by verifying the places of destruction and their shapes, although in special cases, it is possible to know the destruction mode when destruction occurs.