fig1 on the back side of the main board 110 three flat cable connectors 113 are mounted so as to correspond to the three flat cables 140 respectively the flat cables 140 are connected to the flat cable connectors 113 respectively here in order to connect the flat cables 140 to the flat cable connectors 113 respectively in assembly of the main unit 20 leading ends of the flat cables 140 have to be moved in a direction of connection to the flat cable connectors 113 indicated by arrows e in fig1 in other words in longitudinal directions of the flat cables 140 conventionally above operations are often performed by positioning the flat cables by temporarily fixing the flat cables to the housing or the like with tapes and then connecting the flat cables to the connectors by moving the leading ends of the flat cables in the longitudinal directions such a method requires some margins in length between the temporary fixing positions and the leading ends for allowing an operator to perform the operation by moving the leading ends as a result the lengths of the connected flat cables turn out to be redundant accordingly there arises a problem that such redundancies hinder the assembly operation of the electronic device after connection of the flat cables and thus workability is lowered therefore in this embodiment flat cable holding sections 21 a for holding the flat.