A plasma generator includes a gas supply member configured to supply source gas and a plurality of electrodes for generating plasma using the source gas. The plurality of electrodes have a long rod shape in a first direction and are arranged abreast in a second direction vertical to the first direction to be spaced apart from each other at the same height. A spaced distance between electrodes is adjusted by means of a distance adjusting unit including a first connector connected to a first electrode, a second connector connected to a second electrode, and a first shaft pin connecting the first and second connectors to each other. The first and second connectors rotate on the first shaft pin to adjust a spaced distance between the first and second electrodes.