To provide a current sensor which is readily assemblable, without having to greatly change the shape of a magnetism collection core itself, according to the range of the current to be measured, and to provide a watt-hour meter that uses the current sensor.

In this current sensor including the magnetism collection core 8 comprising a magnetic body provided on the periphery of a current bar 7, the magnetism collection core 8 is constituted so as to have two gap surfaces 11a, 11b arranged at a prescribed interval; and the current bar 7 is arranged in the magnetism collection core 8, and a magnetometric sensor 9 for detecting a magnetic field generated between the gap surfaces 11a, 11b by the current flowing in the current bar 7; and sensitivity adjustment members 10a, 10b for adjusting the sensitivity of the magnetometric sensor 9 are arranged between the gap surfaces 11a, 11b.