A lip cosmetic applicator device (1) including an applicator (2) for applying a cosmetic (4) to a lip and a receptacle (3) for containing the cosmetic (4). The applicator (2) is withdrawable from and insertable into the receptacle through a neck (33) of the receptacle (3). The applicator (2) includes a stem (22) and an applying portion (21) connected to one end of the stem (22). The applying portion (21) is a flattened shape and has an applying side (21A) for applying the cosmetic (4). When viewed from the front, the applying portion (21) has a widest part (21E) and gradually decreases in width from the widest part (21E) to a tip thereof. The applying side (21A) of the applying portion (21) is a concave surface having a concavity (21C) in a center thereof.