An electronic control circuit susceptible to heat damage is housed in a first compartment of a body of an electrical connection box. A relay box and a fusible link box which release heat are housed in a second compartment of the body. A cover for covering the body is similarly divided. Air is exhausted from the space through an intake pipe. Wire harnesses connected with the components are inserted through waterproof grommets. Heating of the electronic control unit by the engine and by the heat releasing components is minimized, and waterproofing is achieved.