An impedance calibration circuit includes a first variable impedance, a second variable impedance, a third variable impedance. The first variable impedance is connected to a ZQ terminal. A first control circuit performs a first impedance calibration on the first variable impedance based on an output signal from an output of a first comparator. A second control circuit performs a second impedance calibration on the third variable impedance based on an output signal from an output of a second comparator. A first switch connects an input of the first comparator to one of the ZQ terminal and the first node. A second switch connects the output of the first comparator to one of the first and second control circuits. A third switch connects an output of the first switch to one of first and second input terminals of the first comparator and connects the reference voltage to the other.