A piping connection structure which assigns a function to restrict a pipe body from coming off to a member other than a resin tube, improves in sealing performance and can suppress the amount of fuel permeation. A resin tube comprises a tube body portion; a first diameter-expanding portion formed to increase in diameter from an axial end of the tube body portion and axially positioning seal members by holding the seal members in an axial gap with a retainer; and a second diameter-expanding portion formed to further increase in diameter from the first diameter-expanding portion, and to contact an outer circumferential side of the seal members and be connected to the retainer while in contact with the retainer. Thickness of the first diameter-expanding portion is equal to or greater than thickness of the tube body portion.