A liquid medium plasma discharge generating apparatus includes a main body; a power electrode, provided at one side within the main body, for receiving electric power; a diaphragm member provided within the main body, and consisting of a dielectric defining one or more holes or slits; and a liquid medium charged inside the main body, wherein a ground electrode may be further provided in the main body, opposite the power electrode with the diaphragm member therebetween, whereupon the diaphragm member is arranged contacting the ground electrode.