A signal transmission cable includes a signal line, an insulation layer covering the signal line, and a shield layer covering the insulation layer. A first oxygen amount A1 on an outer peripheral surface of the insulation layer is 1.2 times or greater than a second oxygen amount A2 inside the insulation layer, or a contact angle on the outer peripheral surface the insulation layer is 130° or less, or an adhesion-wetting surface energy on the outer peripheral surface the insulation layer is 27 mJ/m2 or greater, or a first amount of a hydroxy group on the outer peripheral surface of the insulation layer is greater than a second amount of a hydroxy group inside the insulation layer.