A medical procedure through a natural body orifice according to the present invention includes: introducing a first device having an insertion portion, from a patient's natural orifice into a hollow organ; performing a first medical procedure using the first device; withdrawing the first device from the body, and introducing a second device having an insertion portion, from a patient's natural orifice into the body; and performing a second medical procedure using the second device, wherein the first medical procedure is performed prior to the second medical procedure for performing the second medical procedure.