To provide an input capacitance measuring circuit which is capable of measuring at a high speed an input capacitance to a pin electronics part from a probe card of a semiconductor testing device.

The input capacitance measuring circuit measures the input capacitance to the pin electronics part 201 from a device interface part to which DUT is connected directly. The circuit has a waveform generating part 110 which is provided in the device interface part and outputs a square wave signal through the medium of a known output resistance 8, and a capacitance measuring part 12 which is provided in the pin electronics part 201 and measures the input capacitance, based on an input signal waveform of the pin electronics part 201 on which an output signal of the waveform generating part 110 is impressed.