To provide a joint structure for a resin tube not requiring nuts.

Resin tubes 14b, 14a are respectively inserted from right and left directions of a joint body 10, and each tube end face abut on vertical walls formed on outer sides of diameter large parts 10a, 10b. Diameter large part outer circumference faces of sleeves 12a, 12b are the same outer diameter as the diameter large parts 10a, 10b, and their inner diameters are substantially the same as a tube outer diameter. Engagement parts 16a, 16b are mounted for maintaining abutting states of the sleeve end faces to the vertical walls of the joint body. The engagement parts are regulated in inner side periphery parts of openings to prevent relative movement in axial directions of both large diameter parts by providing the openings 18 and fitting the sleeves and both large diameter parts of the joint body in the openings.