A 30-m-long X-ray beam line has been built at the Institute of Space and Astronautical Science (ISAS) to evaluate the performance of X-ray optical instruments for space programs, in particular for the X-ray telescope on-board the Astro-D (Asca) satellite. This beam line consists of an X-ray generator, a 30-m-long vacuum duct, and measuring chambers. Strong and stable X-ray pencil beams from Al, Ti, Cu, Mo and W targets are available with the parallelism of several arcs [full width at half maximum (FWHM)]. Three kinds of detectors are prepared: a conventional gas proportional counter equipped with a thin plastic window, a one-dimensional position-sensitive proportional counter with a Be window, and a charge-coupled device (CCD) modified for X-ray measurements. At the present compact beam line, instead of giant systems of hundreds of meters, the combination of a strong X-ray (0.2-10 keV) pencil beam and translation stages enables us to examine the entire aperture of large X-ray optical instruments of up to 40 cmphi and 1 m in length.