The object of this patent is a device for fitting seats to the chassis of baby carriages. It comprises an anchoring mechanism at each side of the seat for securing the seat in corresponding recipient elements on the chassis of the baby carriage, characterized in that the recipient element is composed of a junction box into which the anchoring mechanism fits. This box rotates around a transverse shaft and has means to limit said rotation. The device can incorporate seats requiring a specific inclination for correct folding.