A tunnel device includes a base portion, a shaft to be connected to the base portion at one end of the shaft, and a tip portion to be connected to another end of shaft. The base portion is provided with a shaft connection portion to which the one end of shaft is connected. The shaft is provided with a shaft-side screw portion at the one end of the shaft. The shaft connection portion includes a shaft housing portion having an inner diameter substantially same as an outer diameter of the one end of the shaft, and a base-portion side screw portion provided on a further inner side relative to the shaft housing portion. The base portion and the shaft are fixed to each other by screwing between the shaft-side screw portion and the base-portion side screw portion.
