PURPOSE: To enable measurement of physical quantity of an object to be measured even with the shapes of a pipe, bar and filament, by arranging a space portion for placing the object being measured at the center of a projection of a cylindrical microwave hollow resonator.

CONSTITUTION: A space portion 3 for setting an object 2 to be measured is arranged at a projection 4 of a cylindrical microwave hollow resonator 1. The projection 4 is so positioned as to be parallel with the object 2 being measured, which makes a dense electric field from near the tip of the projection 4 distribute paralleling the object 2 being measured. This allows the object 2 being measured to be at the center of the space portion 3 with the largest electric field thereby enabling accurate measurement of even a filament-like slender object 2.