We have proposed a new type of vacuum gauge using a palladium (Pd) thin film as a photo-cathode for measuring vacuum pressure. A photo-induced electron was adopted in place of the thermoelectron used in a conventional ionization gauge. The Pd thin film photo-cathode was prepared on a quartz substrate using the ion-beam sputtering method. It was irradiated by ultra violet (UV) light from a deuterium lamp. The photoelectron current emitted from the Pd thin film increased with decreasing film thickness. A maximum current of 240 nA was obtained from a film of 4 nm-thickness. It was found that the ionization gauge with the Pd photo-cathode at 7 nm thickness showed a linear response in the pressure range of 10(-2)-10 Pa in an Ar gas atmosphere. The photoelectric emission from the Pd surface by UV irradiation is affected by the sputtering conditions.