An AD converter includes: a reference voltage generator circuit having a plurality of resistors connected in series with predetermined reference voltage applied to both ends thereof, the reference voltage being divided at connecting points between the individual resistors to generate a plurality of reference voltages; a voltage comparator circuit configured to compare the plurality of reference voltages and analog input signals for conversion into predetermined comparison output signals; and a variable voltage circuit connected to the connecting points of the reference voltage generator circuit and provided with a control signal input terminal inputted with control signals, configured to set an output voltage to be outputted to the connecting points at a predetermined value based on the control signals.