PURPOSE: To obtain the even electromagnetic conversion characteristics in the processing for the throat height, by applying a magnetic flux to a magnetic head to be processed from outside to measure the characteristics of the head and calculating the processing amount from said measured value.

CONSTITUTION: A magnet 6 is provided outside a gap 4, and an impulsive current of an optional fixed level is supplied to the magnet 6. Thus the voltage is induced to a coil 3, and this voltage can be converted into the throat height δ with measurement of its level. Therefore it is possible to calculate a processing amount to obtain the height δ where the prescribed electromagnetic conversion characteristics can be obtained. A magnetic head is processed based on the obtained processing amount. This ensures the even electromagnetic conversion characteristics of the magnetic disk. In the case of a thin film head, the voltage induced at the coil 3 is measured in the same way. Then the throat height δ is obtained from the electromagnetic conversion characteristics to calculate the processing amount and the inclination of a substrate 1. Thus the simultaneous processing is possible with a thin film head.