To reduce weight in a lithium ion battery protective circuit.

In this lithium ion battery protective circuit having a resin base board 51 mounted with electronic parts 54 to 58, terminals arranged on both ends of an electronic part mounting surface of this resin base board, and a waterproof resin 59 for covering the whole surface on the electronic part mounting surface side of the resin base board, the lithium ion battery protective circuit and a manufacturing method therefor can impart strength by the resin base board and the waterproof resin by enhancing hardness of the waterproof resin up to that of the resin base board or further higher, and can more sharply reduce the weight than when imparting the strength by the thickness of the resin base board.