An object of the present invention is to provide an electrical connection box in which reduction in weight can be achieved by simplification of the construction, while preventing short-circuiting of a positive electrode side busbar and a negative electrode side busbar. An electrical connection box includes: a positive electrode side busbar connected to a positive electrode of a battery; a negative electrode side busbar connected to a negative electrode of the battery; and a case in which the positive electrode side busbar and the negative electrode side busbar are accommodated. The case includes: a bottom wall; a circumferential wall erected from the bottom wall; and a partition wall erected from the bottom wall. The partition wall is a waterproof partition that partitions a positive electrode side busbar accommodating area and a negative electrode side busbar accommodating area.