Abstract: An apparatus for measuring physical quantities comprises a microwave cavity resonator (1) provided with a protrusion (4) on its axis. An object (2) to be measured is placed in the central portion (17) of the protrusion (4) in parallel with it, or the object (2) to be measured is placed vertically against the protrusion (4), so that an electric field can be confined to the area to be measured. This results in precise measurement of physical quantities on a minute portion of the object to be measured. A method of measuring physical quantities comprises obtaining moisture content x (g/m.sup.2) and basis weight y (g/m.sup.2) of the object to be measured from equations having at least a product term of moisture content x and basis weight y, and by measuring the frequency and the voltage of microwave energy at the maximum resonance point on the object to be measured. This enables obtaining easily and accurately the moisture content and basis weight of the object to be measured.