A breast pump includes a milking port which can accommodate a breast, a storage for storing breast milk extracted from the breast, and a milking unit including a tongue section which can press the portion near an areola of the breast, and is configured in such a manner that the peak of the tongue section of the milking unit can be moved continuously in the direction away from the side of the milking port, and the height of the tongue section can be varied by independent movements of a plurality of sections of a deforming device from the side of the milking port to the inner side.