An integrator according to an embodiment includes first and second nodes, first to fifth switches, first and second main integration capacitors, and a first subsidiary integration capacitor. The first (second, third, fourth, fifth) switch has one end connected to a first (third, first, fourth, first) node and the other end connected to a third (second, fourth, second, fifth) node. The first main integration capacitor has one end connected to the third node and the other end connected to a standard voltage line. The second main integration capacitor has one end connected to the fourth node and the other end connected to the standard voltage line. The first subsidiary integration capacitor that has one end connected to the fifth node and the other end connected to the standard voltage line.