An in-vehicle electronic device includes a circuit board in which a preamplifier circuit, and the like are provided, and a holding case, which stores the circuit board. The holding case is configured by combining a lower case which is fixed to a glass surface in which an antenna radiation conductor is arranged, and an upper case which is detachably mounted on the lower case so as to cover the lower case, so that a connection terminal held in the lower case is brought into press-contact with an electrode of the circuit board. When the upper case is removed from the lower case, an elastic piece is bent by pushing a tip of a protruded portion to a base end side, or a snap claw is separated from a locking hole by inserting a tool such as a driver, in between a tongue piece and the elastic piece.