A compact soft x-ray reflectometer usable in a small laboratory is developed for measurement of the soft x-ray reflectance of a multilayer mirror in a wide wavelength range, i.e. , including the water window (23 to 44Å). In this reflectometer, the reflectance can be measured as a function of wavelength or incidence angle. A laser-produced plasma soft x-ray source, which is small but has high brightness, makes it possible to construct the compact soft x-ray reflectometer. The soft x rays generated by the source are monochromatized with a grazing incidence reflection grating. Incidence angle dependency of the reflectance can be measured from 2 deg (almost normal incidence) to 85 deg. Reflectances of a Ni/Ti multilayer and a Mo/Si multilayer are measured, and 10.9% at a wavelength of 40.8Å and an angle of 75.1 deg and 38% at a wavelength of 135.5Å and an angle of 25.7 deg from normal incidence are obtained, respectively.