An electromagnetic wave measuring method is provided that is capable of performing high-precision measurement in a shorter time and in a greater variety of frequency bands than heretofore with a comparatively simple configuration. A plate-like antenna (13) of which the outline shape of an opposed surface opposite a measured object (5) is similar to the outline shape of an opposed surface of the measured object (5) is brought close to the measured object (5), and an electromagnetic wave from the measured object (5) is measured based on the frequency spectrum of a received signal received by the plate-like antenna (13).