A flash A/D converter includes a reference voltage generator for generating a plurality of reference voltages, a first group of amplifiers having a plurality of amplifiers each of which amplifies a difference voltage between each reference voltage generated by the reference voltage generator and a voltage of an input signal, and a second group of amplifiers having a plurality of amplifiers. Each amplifier of the first group of amplifiers is a differential amplifier having a different pair formed of a plurality of sets of cascade-connected transistors, and has a first switch for short-circuiting respective cascade connection portions of the plurality of transistors configuring the differential pair. Each amplifier of the second group of amplifiers is a differential amplifier having a differential pair formed of at least two transistors and has a second switch for short-circuiting a portion between input units of the differential pair. The first switch and the second switch are controlled to open and close by a control clock of a predetermined period.