In a flexible board including laminated resin layers containing the same thermoplastic resin as a principal material, a rigid portion includes a region in which a first resin layer is disposed between a second resin layer defining an upper principal surface and a third resin layer defining a lower principal surface so that the rigid portion has a large thickness, and a flexible portion includes a region in which the first resin layer is not disposed between the second and third resin layers so that the flexible portion has flexibility, a step portion at which a thickness changes is between the rigid and flexible portions, and the second and third resin layers extend in a region from the rigid portion beyond the step portion to the flexible portion.