To provide a drain hose connecting structure for easily and reliably connecting a drain hose which discharges drain from an air-conditioner to the outside, to a drain discharge port of a drain pan of the air-conditioner in a non-extractable manner.

A male screw 3 is provided on the outer peripheral face of the drain discharge port 1 and a lock protrusion 4 having an inclined top face 4a and a lock end face 4b is protruded on the terminal end of the male screw 3. On the other hand, a female screw 5 screwed to the male screw 3 is provided in a one-end opening portion of the drain hose 2 and a lock recessed portion 6 fitted and locked to the locking protrusion 4 is formed at the tip of the female screw 5. After a one-end opening of the drain hose 2 is fitted to the drain discharge port 1 with the female screw 5 screwed to the male screw 3 until the lock recessed portion 6 reaches the lock protrusion 4, the lock recessed portion 6 is locked to the lock protrusion 4 while sliding on and riding over the lock protrusion 4.