[Problem] To provide a wiring substrate having high mounting reliability and an electronic device using same. [Solution] This wiring substrate comprises: an insulated substrate (2) having a side surface including a cut-out section (3); and an external electrode (4) disposed from the inside surface of the cut-out section (3) to the bottom surface of the insulated substrate (2). The cut-out section (3) reaches the bottom end of the insulated substrate (2) and a bottom end section of the inside surface of the cut-out section (3) protrudes towards the inside direction of the cut-out section (3).