To provide a door structure to secure a step-over passage space by expanding/contracting or sliding down a part of a pipe fence within a surface of a gate frame in a door to be the passage.

The figure shows a sliding mode of a sliding door frame 13 and fence pipes 21. It shows that about one-thirds of a center part of an upper horizontal frame 10 is separated from the upper horizontal frame 10 to become a sliding door frame 13 which slides down along right and left each two fence pipes 21 and two central pipes are pushed down to move the center part of the gate to height 25 cm from a floor by expanding/contracting in three steps to form a passage space which can be easily stepped over.