The present invention relates to an electronic control device which is an electronic control device such as an engine ECU for a vehicle and has a tight sealing structure between a case and a connector. The present invention provides an electronic control device for a vehicle, which implements a new type of sealing manner in which a space to be filled with a sealing material is formed between a case side dam and a connector side dam when a case and a connector of the electronic control device are assembled, and the sealing material is applied in the space, which is formed as described above, such that airtightness for an assembly region between the case and the connector is maintained, thereby securing sufficient sealing areas because of enlarged sealing sections, and achieving stable sealing quality and improving quality.