In a reset period of a first stage, a switching circuit is turned on, and high-level driving voltages are output from driving circuits. In a charge transfer period subsequent to the reset period, the switching circuit is turned off, and low-level driving voltages are output from the driving circuits. It is determined whether or not an output voltage of an amplifier circuit in the charge transfer period is included in a normal range. In the inspection of a second stage subsequent to the first stage, in the same manner as in the normal measurement, voltages having opposite phases are output from the driving circuits in the reset period and the charge transfer period, and it is determined whether or not the output voltage of the amplifier circuit in the charge transfer period is included in a normal range.