A cannular tube is configured to insert a distal end side thereof into a body cavity to secure an insertion passage through which a medical forceps is introduced from a proximal end side thereof into the body cavity. The overcoat tube includes a distal end-side tube member forming the insertion passage at the distal end side, a proximal end-side tube member forming the insertion passage at the proximal end side, and an intermediate coupler that couples the distal end-side tube member to the proximal end-side tube member so that the distal end-side tube member is capable of being tilted in two axial directions centered on a pivotal center with respect to the proximal end-side tube member and connects the insertion passages of the distal and proximal end-side tube members.
