A pacifier for use by an infant hospitalized in a neonatal intensive care unit and comprising: a nipple portion for being held in a mouth of the infant; and a back plate portion that is connected to a base portion of the nipple portion and has an asymmetrical shape with respect to an axis passing through a center of the nipple portion and extending in a vertical direction connecting a nose and the mouth of the infant in a state where the infant holds the pacifier in its mouth, wherein the back plate portion includes: a main body portion connected to the base portion and having a shape extending in the form of a flange from the base portion to a periphery of the base portion; and an extension portion that is connected to the main body portion, characterised in that: the extension portion is connected to the main body portion on only one of a left side or a right side of the main body portion in a lateral direction, wherein the lateral direction is perpendicular to the vertical direction and connects left and right cheeks of the infant in the state where the infant holds the pacifier in its mouth, the extension portion extends from the main body portion in the lateral direction only on the one of the left side or the right side of the main body portion, and the extension portion is inclined toward the side of a tip portion of the nipple portion as the extension portion extends from the main body portion. a nipple portion for being held in a mouth of the infant; and a back plate portion that is connected to a base portion of the nipple portion and has an asymmetrical shape with respect to an axis passing through a center of the nipple portion and extending in a vertical direction connecting a nose and the mouth of the infant in a state where the infant holds the pacifier in its mouth, wherein the back plate portion includes: a main body portion connected to the base portion and having a shape extending in the form of a flange from the base portion to a periphery of the base portion; and an extension portion that is connected to the main body portion, characterised in that: the extension portion is connected to the main body portion on only one of a left side or a right side of the main body portion in a lateral direction, wherein the lateral direction is perpendicular to the vertical direction and connects left and right cheeks of the infant in the state where the infant holds the pacifier in its mouth, the extension portion extends from the main body portion in the lateral direction only on the one of the left side or the right side of the main body portion, and the extension portion is inclined toward the side of a tip portion of the nipple portion as the extension portion extends from the main body portion. a main body portion connected to the base portion and having a shape extending in the form of a flange from the base portion to a periphery of the base portion; and an extension portion that is connected to the main body portion, characterised in that: the extension portion is connected to the main body portion on only one of a left side or a right side of the main body portion in a lateral direction, wherein the lateral direction is perpendicular to the vertical direction and connects left and right cheeks of the infant in the state where the infant holds the pacifier in its mouth, the extension portion extends from the main body portion in the lateral direction only on the one of the left side or the right side of the main body portion, and the extension portion is inclined toward the side of a tip portion of the nipple portion as the extension portion extends from the main body portion. the extension portion is connected to the main body portion on only one of a left side or a right side of the main body portion in a lateral direction, wherein the lateral direction is perpendicular to the vertical direction and connects left and right cheeks of the infant in the state where the infant holds the pacifier in its mouth, the extension portion extends from the main body portion in the lateral direction only on the one of the left side or the right side of the main body portion, and the extension portion is inclined toward the side of a tip portion of the nipple portion as the extension portion extends from the main body portion.