A rotorcraft and a connecting structure for an arm and an airframe of a rotorcraft are provided. The connecting structure includes: a fixed sleeve pipe configured to extend out from a circumferential edge of the airframe; an insertion head configured to be disposed to the first end of the arm and configured to be inserted into the fixed sleeve pipe; a lock sleeve configured to be fitted over the arm and having an insertion portion configured to be embedded into the insertion groove; and a lock nut configured to be fitted over the arm and configured for being in threaded connection with the fixed sleeve pipe.