Described herein is an electrical connection box. In certain aspects the electrical connection box includes a case; a circuit board disposed inside the case; and a connector housing disposed in an opening surrounded by an opening edge portion of a side wall of the case. In certain aspects, the opening edge portion can have a first opening edge portion, a second opening edge portion, and an arcuate notch in which the arcuate notch is configured to reduce, prevent, or inhibit entry of water into the connector housing.