A flexible board includes a first sheet section including a first principal surface, a second sheet section including a second principal surface and provided in a different position from the first principal surface in a normal direction to the first principal surface, at least one first bent sheet section configured to connect ends of the first and second sheet sections, the first bent sheet section including a third principal surface not parallel to the first and second principal surfaces, and at least two second bent sheet sections each including a fourth principal surface and provided in different positions from the third principal surface in a normal direction to the third principal surface. The second bent sheet sections are positioned so as to sandwich the first bent sheet section therebetween when viewed in a plan view in the normal direction to the third principal surface.