Rotating shaft descending distance data detection mechanism and substrate processing apparatus equipped with rotating shaft descending distance data detection mechanism with which the accuracy of current detection can be increased and the device can be made small in size and low in cost

Provided is a rotating shaft descending distance data detection mechanism of a substrate processing apparatus, in which the need for a cancel circuit is eliminated, and a converter through which a drill bit penetrates is used to directly detect a current flowing in the drill bit when the drill bit comes into touch with an inner layer to be reached. Furthermore, in addition to part of a high-frequency current from a high-frequency oscillator, the current also includes part of a harmonic current that flows from an inverter through parasitic capacitance to a rotating shaft body, so as to increase the current flowing in the drill bit. Thus, in addition to the increased accuracy of the current detected by the converter, the device can be made small in size and low in cost and, even for processing a sub-substrate having a small area, the current flowing in the drill bit can be reliably detected to correctly process the sub-substrate.