A wiring board assembly (1) includes: a flexible printed wiring board (2) which includes at least an insulating substrate (5) including a through-hole (53), and wiring patterns (61) and (62) provided on the insulating substrate (5) and extending to peripheral edge portions (531n) and (532n) of the through-hole (53); a metal reinforcing plate (3) attached to the flexible printed wiring board (2) and facing the through-hole (53); and a solder connection portion (4) covering an inner wall surface (534) of the through-hole (53) and electrically connecting the wiring patterns (61) and (62) to the metal reinforcing plate (3).