TUBE FITTING AND TUBE EQUIPPED WITH TUBE FITTING

There is provided a tube fitting (1A; 1B) etc. that when fastening and release are repeated, are capable of providing an initial axial force which makes co-rotation torque less than an upper limit value and make it possible to keep the axial force decrease ratio low. A flare nut (FN; 1A) is provided with a resin coating layer (18; 28) that includes a polyethylene based substance, a lubricant, and solid particles. When mass per unit area w (g/m2) is defined as a value obtained by dividing the mass difference between a state with the resin coating layer (18; 28) and a state without the resin coating layer (18; 28) by the surface area of a coated region (R), the mass per unit area w satisfies a relation 0.79