In order to study the radial transport of tungsten ions in long-pulse H-mode discharges, a space-resolved spectrometer working at 30-520 angstrom has been newly developed to measure a radial profile of the tungsten line emission. The spectrometer is installed behind a long extension vacuum tube connected to a horizontal midplane diagnostic port of EAST tokamak. The long distance between the plasma and spectrometer, 8835.5 mm, enables observation of the radial profile of impurity line emissions in a wide vertical range of -8.5 <= Z <= 40 cm (-0.1 <= p <= 0.6). A good spectral resolution of Delta lambda(0) = 4 - 5 pixels at the foot position of spectral line profiles and a high spatial resolution of Delta Z = 2.5 cm are obtained in addition to a sufficient temporal resolution, e.g. 50 ms/frame. As a result, accurate radial profiles have been successfully obtained in EAST Ohmic and H-mode discharges for several impurity species such as carbon, oxygen, argon, iron and tungsten. The radial profiles of tungsten line emissions from W42+ -W45+ ions with 4p-4s transitions measured at two wavelength ranges of 45-70 angstrom and 120-140 angstrom are analyzed for the ion density evaluation based on the photon emissivity coefficient from ADAS database. The result shows that the density of W43+-W45+ ions ranges at 2-6 x 10(8) cm(-3) in steady H-mode discharges with T-e(0) = 3 keV and n(e)(0) = 4 x 10(13) cm(-3).