This gas production system includes: a gas production device having a reactor forming a flow path for a treatment target gas, a first electrode and a second electrode to which voltage is applied, and a catalyst layer provided in the flow path and containing a catalyst; voltage generation means for generating voltage to be applied to the first electrode and the second electrode; and gas supply means for supplying the treatment target gas to the gas production device. The voltage generation means has frequency setting means for setting the frequency of the voltage in accordance with the treatment target gas, plasma generated between the first electrode and the second electrode is applied to the catalyst layer, and the treatment target gas is reformed to obtain a product gas.