A current sensor is disclosed which detects current values of bus bars through which three phase alternating currents flow, including shields which are provided for each of the bus bars, a flat board on which magnetic detecting elements corresponding to respective phases are mounted, and a housing inside which the shields and the board are accommodated, wherein the housing is formed with storage parts to store the shield, the board is formed with concave parts recessed in a direction opposite to the direction the board is assembled, the shields are formed with cut parts recessed in the direction the board is assembled, at parts that intersect with the board when the shields and the board are accommodated, and when the shields and the board are accommodated, a part of the board is located in the cut parts, and a part of the shields is located in the concave parts.