To reduce periods and time and effort in the case of electromagnetic wave measuring.

A turntable 2 which autorotates an object 7 to be measured for reflection around an axis perpendicular to a floor surface, a rail 11 stretched on a floor surface while maintaining an almost constant distance from the center of the turntable 2, a transmitting antenna 10 which can move along the rail 11, and a fixed receiving antenna 6 are installed in an electromagnetic wave dark room 1. A rotation angle of the turntable 2 is so adjusted that normal 7b of a reflecting surface 7a of the object 7 and normal 6b of an aperture surface 6a of the receiving antenna 6 make a specified angle θ. The amount of reflection is measured by adjusting a position of the transmitting antenna 10 in such a manner that an angle between the normal 7b of the reflecting surface 7a of the object 7 and normal 10b of an aperture surface 10a of the transmitting antenna 10 becomes equal to the specified angle θ.