A wired circuit board that can prevent inconsistency in characteristic impedance to allow effective transmission of electrical signals from a magnetic head to a control board portion. A wired circuit board is constructed so that a suspension board portion for supporting the magnetic head and a control board portion for controlling the magnetic head are formed to be continuous and integral with each other. To be more specific, a first conductor layer connected to the magnetic head in the suspension board portion and a second conductor layer connected to a preamplifier IC in the control board portion are formed from the same material and formed on a common insulating base layer simultaneously. Further, a common insulating cover layer to cover the first conductor layer and the second conductor layer is formed on the common insulating base layer.