To measure a spatial image with full accuracy.

A slit 22, which extends in Y-axis direction, having a width in the measurement direction (X-axis direction) less than (wavelength λ/opening number N.A. of a projection optical system), is formed in a slit plate 90 of a spatial image measurement apparatus 59. When a specific pattern PM illuminated with an illumination light IL for this purpose and when the slit plate 90 is scanned in X-axis direction to the spatial image, in a state in which the spatial image of that pattern is formed on the image surface by way of a projection optical system PL, the light having transmitted the slit 22 during scanning is photoelectrically converted with a photoelectric converter element 24. The photoelectric conversion signal (signal which corresponds to the light intensity of the spatial image) is output. Then based on the photoelectric conversion signal, light intensity distribution corresponding to the spatial image is measured with a controller. In this case, the spatial image can be measured with practically sufficient accuracy, since the width of the slit 22 is equal to or less than (λ/N.A.).