PROBLEM TO BE SOLVED: To provide an endoscope easily assembled and including an inexpensive fitting structure of a branch member, and a method for assembling the branch member of the endoscope.SOLUTION: A branch member 31 in a base end side cylindrical member 29 of an insertion part 2 includes: a constituent wall part 34a of a first passage 31a a constituent wall part 34b of a second passage 31b and a connecting part 34c removably connected to the cylindrical member 29. The cylindrical member 29 has an opening part 30 penetrating through the constituent wall part 34b of the second passage 31b of the branch member 31, and a guide groove part 36 communicated with the opening part 30. The guide groove part 36 is provided with a first regulating part 37 for regulating the axial movement of the branch member 31 and a second regulating part 38 for regulating the rotation around the axis of the branch member 31. The connecting part 34c includes: a first engagement part 39 moved in the direction orthogonal to the axial direction to engage with the first regulating part 37 and a second engagement part 40 moved in the axial direction to engage with the second regulating part 38.
