An ultrahigh-vacuum scanning tunneling microscope (UHV-STM) combined with an x-ray source has been developed. STM samples were irradiated with an x-ray beam and an x-ray induced photoemission current was detected with the tip. By using the system, apparent height increases due to the x-ray induced current were successfully observed in STM images of Cr/Cu(111), Au/Cu(111), Si(111)7x7, and Si(111)-5x1 Au surfaces. A bias voltage applied to the tip enhances collection of the x-ray induced current and increases the apparent height. The relative height increase of the Au overlayer to the Cu substrate in the STM images of the Au/Cu(111) surface was found to depend on the x-ray irradiation, suggesting that it may be a promising tool for elemental analysis in a STM.