To provide a ventilation adjustment structure for eliminating negative pressure upon feeding milk and preventing the leak of milk.
In a feeding bottle including a nipple 2 made of an elastic material, a feeding bottle body 1, and a cap 3 mounting the nipple 2 to hold between an opening part of the feeding bottle body 1 and itself, a ventilation adjustment structure is obtained in such a manner that a flange part 24 that can be placed on a top surface of the opening part of the feeding bottle body 1 and has a diameter slightly larger than the maximum diameter of the top surface is formed at the lower end part of the nipple 2, a V shape groove 24a is arranged by depression in a ring shape over a whole circumference on the upper surface of the flange part 24, a flat open part 24b continuing from the bottom of the V shape groove 24a is formed in an external direction of a part of the groove, a ventilation groove 24c is arranged by depression in a diameter direction on a lower surface of the flange part 24 corresponding to the open part 24b, and the other hand, a ring shape projected line rib 32a fittable into the V shape groove 24a is provided on a lower surface of an inward flange 32 arranged in the cap 3.