This paper reports on the discussion of the effect of pressure behind the shock wave induced by the thin silver wire explosion on the particle size distributions generated in the electric explosion of wire (EEW) and the pulsed wire discharge (PWD) methods in the atmosphere. EEW and PWD were generated by the pulsed discharge with the charged voltage of 5.5 and 14 kV in the capacitor of 2.4 μF for the wire, respectively. The phenomena of EEW and PWD and the propagation shock waves emitted by the wire explosions in these methods were visualized optically. The visualized images indicated that the exploded wire with particles expanded behind the shock wave. The pressure of shock waves was calculated theoretically using the wave velocity analyzed with the visualized images. The maximum pressure of shock wave in PWD was higher than that in EEW. The range of particle size distribution generated by PWD was narrower than that by EEW. These results suggested that the finer powderzation with narrower-range particle distributions at PWD was generated by the higher pressure behind the shock wave.