A current sensor includes a housing having a pair of first slits, a bus bar supported by the housing and electrically connected to a battery post provided on a battery, an annular shield member arranged so as to surround an axis extending in a direction in which a current is flowed in the bus bar, and a magnetic-electric conversion element provided on the housing to detect a magnetic flux density of a magnetic field generated when the current is flowed in the bus bar and produce an electric signal. The magnetic-electric conversion element is arranged between the first slits. The shield member is inserted into the first slits so that the shield member is mounted on the housing.