A compact, inexpensive static induction thyristor (SIThy) which is less likely to be broken down at a high voltage rise-up rate during operation and which is used in a high-voltage pulse generator capable of generating a high-voltage short pulse is provided. Thicknesses and impurity concentrations of a base region and a buffer region are determined such that a peak voltage obtained by a peak current at which a punch-through state is brought about does not exceed a breakdown voltage of the SIThy. Such design can achieve an SIThy having a self protecting function of autonomously preventing its breakdown without compromising a turn-on performance in which the peak voltage does not drastically exceed the breakdown voltage of the SIThy even when the peak current increases. Further, a compact SIThy capable of generating a short pulse can be achieved by reducing a gate-channel current-carrying area to a minimum.