In X-ray fluorescence (XRF) analysis, which has been used to analyze elements in various samples, it is important to decrease the background (BG) intensity. Generally, BG signals are reduced by inserting metal foils of various types and thicknesses between the X-ray tube and sample as primary X-ray filters. In this study, we developed a unique gas filter-XRF (GF-XRF) instrument to easily reduce the BG effect by changing the pressure of the gas to ensure that the absorption edge of the gas element is slightly lower than the energy of the XRF peak of the target element. The advantage of using a gas is that the gas pressure can be altered easily. To evaluate the performance of this instrument, Ti and Zr were selected as target elements, and Ar and Kr were selected as the filtering gases. When the XRF spectra of the Ti sample were recorded using the Ar gas filter, as the Ar gas pressure increased, the background signal in the energy region of the Ti Kα peak decreased, resulting in an increase in the signal-to-noise ratio (SNR) of that peak. When the Kr gas filter was used, both the SNR and the minimum detection limit of Zr improved. These results demonstrate that the unique GF-XRF instrument is useful for high-sensitivity analyses.