The invention proposes a device (1) and a corresponding method, wherein the device (1) comprises: a first element (10) to be attached to a breast of a breastfeeding mother; and a first marker (11) located on the outer surface (100) of the first element (10), wherein the first marker (11) is used for indicating a position of a mother's breast that the baby's lip is expected to contact in order to correctly hold the mother's breast. With the device (1) attached to the mother's breast, the first marker (11) indicates a position that the baby's lip is expected to contact, and the breastfeeding mother can have a clear view of whether the baby correctly holds the mother's breast according to the distance between the first marker (11) and the baby's lip.