To provide a magnetic core by which combination strength between divided cores is sufficiently obtained when the magnetic core is formed by combining the divided cores, and which can be manufactured at low cost, and a magnetic balance type current sensor which has excellent measurement accuracy and can be manufactured at low cost.

A magnetic core is constituted by combining a plurality of divided cores 1A and 1B. The divided cores 1A and 1B have: first trunks 12A and 12B; second trunks 14A and 14B; third trunks 13A and 13B. When the divided cores 1A and 1B are combined with each other, the first truck 12A contacts the second trunk 14A, the first trunk 12B contacts the second trunk 14B, and at least one end of the first trunk 12A and the second trunk 14A engages into the corresponding end of the first trunk 12B and the second trunk 14B.