PROBLEM TO BE SOLVED: To provide a guide tube device for moving a measurement position on an measurement object in a state that the observation visual field of an endoscope is fixed.SOLUTION: This guide tube device 5 equipped with a channel 4 for inserting an insertion part 2 of an endoscope 3 for observing a visible light beam includes: a tube body 40 having a tube top end 42 positioned at the top end of a curved part 14 formed at the insertion part when a base end side is mounted on the insertion part a measurement part having a light emission part 51 for irradiating an irradiation object area W1 with a visible light beam, and for making, visibly different by an endoscope, the brightness of the visible light beam reflected by the irradiation object area to a section adjacent to the irradiation object area and a reception part 53 for detecting the visible light beam from a prescribed receiving direction D, which measures a distance to the irradiation object area and an adjustment part 48 for adjusting the direction of the light emission part and the reception part to the tube top end so that a direction going from the irradiation object area to the reception part can be set to the receiving direction. The light emission part and the reception part are connected to the tube top end.
