Abstract: A tapped hole measuring apparatus available for automatically measuring the major diameter, minor diameter, effective diameter and depth of a tapped hole. The apparatus comprises a measuring stylus with at least two air discharging ports which can take inserting movement into the tapped hole. The apparatus separately measures the variations of the back pressures of air supplied to the air discharging ports, and converts the back pressure variations into electric signals and stores them. Also included in the apparatus is a configuration calculating section for comparing the variation of the electric signal from the tapped hole with a variation of electric signal from a reference tapped hole to obtain the configurational dimensions of the tapped hole being measured.