A current sensor and a current detecting method in which a sensitivity in at least 100 .mu.A region and a dynamic range of 80 dB are achieved through a simple structure. The current sensor comprises one middle leg magnetic circuit (1) having opposite ends, two outer leg magnetic circuit (2a,2b) being connected with one and the other ends of the middle leg magnetic circuit (1), respectively, an exciting means (3a) arranged in the outer leg magnetic circuit (2a) and exciting means (3b) arranged in the outer leg magnetic circuit (2b), a flux detecting, means (4) arranged in the middle leg magnetic circuit (1), means (7) for driving the exciting means (3a,3b), and a detection circuit (8) connected with the flux detecting means (4) and outputting an electric signal interlocked with the flux being detected by the flux detecting means (4).