Abstract: An expandable and retractable positioning device for use in tubular members comprises a first tubular member including a receiving mount received at the rear end thereof and having a control knob fitted at the rear end thereof, for receiving an elongated rack at the front end thereof, and for further inserting the rack into the first tubular member, and a second tubular member fitted in the first tubular member and including a support seat mounted at the rear end thereof and having a through hole formed thereon for the insertion of the rack, and having compartments for communicating with the through hole mounted at the peripheral side thereof and each having a toothed block placed therein. Besides, the toothed block includes engaging teeth arranged on the inner side thereof, such that the adjustable positioning purpose of the tubular members may be obtained.