Abstract: A pacifier 2 includes: a nipple portion 3 held in a mouth of the infant; and a back plate portion 4 that has an asymmetrical shape with respect to an axis 36 passing through a center 35 of the nipple portion 3 and extending in a vertical direction connecting a nose and the mouth of the infant in a state where the infant holds the pacifier 2 in the mouth. The back plate portion 4 includes: a main body portion 41; and an extension portion 42 that is connected to the main body portion 41 on either side of a lateral direction that is perpendicular to the vertical direction and connects left and right cheeks of the infant in a state where the infant holds the pacifier 2 in the mouth, the extension portion 42 extending from the main body portion 41 toward the either side.