A flexible circuit board whose entire surface has flexibility includes a first substrate portion and a second substrate portion that are adjacent to each other and electrically connected to each other in a planar direction of the flexible circuit board. The first substrate portion includes a plurality of resin layers, which are bonded together with an adhesive, and the second substrate portion includes a plurality of resin layers, which are integrated with one another by intermolecular bonding of a thermoplastic resin.