One embodiment provides an electronic control unit including: a base body; a control circuit board that controls electric parts; and a housing that is attached to one surface of the base body. The housing includes an accommodating portion which accommodates the control circuit board thereinside and a flange. The flange includes an attaching hole penetrating therethrough. A part of the accommodating portion is positioned on an extension of a center axis of the attaching hole. An attaching pin projects from the one surface of the base body so as to be inserted into the attaching hole. An attaching portion is formed on the attaching pin so as to be positioned between the flange and the accommodating portion. An elastic member is attached to the attaching portion so as to bias the flange toward the one surface of the base body.