Gallium oxide thin film has properties of n-type semiconductor and it is stable at high temperature. The resistivity of Ga2O3 changes with the concentration of oxygen in the thin film. An oxygen sensor was made on the basis of this principle. Gallium oxide thin film was deposited on the Si substrate from a sintered powder target by a rf magnetron sputtering using Ar as the sputtering gas. The sputtering condition is a very important factor to control the oxygen content of the Ga2O3 thin film and hence the response characteristics of the sensor. In this present paper, an attention was paid on the sputtering pressure of Ar during the film deposition. It has been found that electrical conductivity, gas sensitivity and rising response time of the thin film depends on sputtering pressure of Ar during the deposition process. It has also been clarified that gallium oxide thin film deposited in lower sputtering pressure shows better electrical conductivity and rising response time. whereas the thin film deposited in high sputtering pressure shows higher gas sensitivity The difference in characteristics of the deposited thin films may be considered due to the surface structure as revealed from the AFM observation.