To provide a pipe structure capable of moving up and down a shelf board as a structural element of the pipe structure or changing a sleeve top plate as an accessory of the pipe structure from a horizontal attitude into a vertical attitude.

An expansion mechanism part 4 is constituted by a vertical pipe 2 as a supporting column and a rack pipe 3 which is movably inserted into a lock mechanism cylinder body 5 mounted on the upper-end outer periphery of the vertical pipe 2. The pipe structure 1a is constructed by connecting a lateral beam pipe 9 to the vertical pipe 2 and the rack pipe 3. The lock mechanism cylinder body 5 has a lock mechanism part 6 which engages with rack teeth 3a of the rack pipe 3 to fix the position of the rack pipe 3 or which disengages therefrom to make the rack pipe 3 movable.