A flexible substrate comprises: (i) a film; (ii) an insulating resin layer formed on each of a front face of the film and a rear face of the film, which rear face is opposite to the front face; (iii) a front-sided wiring pattern embedded in the insulating resin layer formed on the front face of the film, and a rear-sided wiring pattern embedded in the insulating resin layer formed on the rear face of the film; and (iv) a via which is located between the front-sided wiring pattern and the rear-sided wiring pattern and serves to electrically interconnect the front-sided wiring pattern and the rear-sided wiring pattern, wherein the insulating resin layer formed on each of the front face and the rear face of the film is thicker than the film.