a drainage structure of an electric parts accommodation box includes a drainage port formed on a bottom wall of the box , a cut - out portion that is continuous with the drainage port , a tip of which tapers off to form an acute angle , and a water - leading groove that is continuous with the tip , formed on an outer surface of the bottom wall . with this , a droplet that sticks to the water - leading groove disposed on the outer surface of the bottom wall is brought into contact with a droplet that sticks to the tip of the cut - out portion disposed on an inner surface of the bottom wall to flow out a droplet that sticks to a peripheral edge of the drainage port to the outer surface of the bottom wall . this more effectively drains liquid droplets that would otherwise remain within the box to reduce current leaks caused by such droplets coming into contact with electrical components in the box , such as closely spaced bus bars .