Provided is an electronic control device, in which positioning of a case including a connector housing portion and a pin header portion of a connector mounted on an electronic circuit board may be carried out easily with high accuracy so that ease of assembly and a water-proof property of the connector are improved. The electronic control device includes: an electronic circuit board (1) on which a pin header (30) used for electric connection to an external device is mounted together with an electronic component (11); and a case (2) for receiving the electronic circuit board therein, the case including a connector housing portion (31) provided as an opening portion (310) at a position corresponding to the pin header. A cover (20) of the case including the connector housing portion and the pin header mounted on the electronic circuit board have a first positioning structure using press-fit.