PROBLEM TO BE SOLVED: To provide a connecting structure in a guide rail for a sliding door of a plastic greenhouse capable of certainly preventing deformation (bending) of the guide rail caused by weight of the sliding door arranged on the guide rail for the sliding door in a suspended state.SOLUTION: A connecting member 3 has a groove structure made of steel which opens downward and holds a peripheral surface of a sliding door guide rail 2. The connecting member 3 also comprises screw holes 40, 40 into which fixing bolts 4 are inserted on upper surface thereof and bolt holes 60, 70 which allow U-bolts 6 (7) pass through on common positions on both side surfaces. Each of end parts of the sliding door guide rails 2, 2 is introduced into the opening inner section of the connecting member 3 from right and left directions so that the end parts locate at the intermediate position of the connecting member 3 and contact each other. Tip ends of the fixing bolts 4 which are inserted into the screw holes 40, 40 are pressed onto the upper surface of the sliding door guide rail 2 so that the position of the sliding door guide rail 2 is fixed. The connecting member 3 is attached to a pillar member 13 with U-bolts 6 inserted into the bolt holes 60, 60.【課題】引き戸用ガイドレールへ懸垂状態に設置した引き戸の重量によって同ガイドレールの変形（撓み）を確実に防止できる、ビニールハウスの引き戸用ガイドレールの連結構造を提供する。【解決手段】連結部材３は、引き戸用ガイドレール２の外周面を抱持する、下向きに開口する溝形鋼状とされ、上面に固定用ボルト４をねじ込むネジ孔４０、４０が設けられ、両側面の共通位置にＵボルト６（７）を通すボルト孔６０、７０が設けられている。連結部材３の開口内部へ、左右両方向から導いた引き戸用ガイドレール２、２の各端部を連結部材３の中間位置まで挿入して突き合わせ、ネジ孔４０、４０へねじ込んだ固定用ボルト４の先端を、引き戸用ガイドレール２の上面へ圧接させて、引き戸用ガイドレール２の位置が固定されている。ボルト孔６０、６０へ通したＵボルト６で、連結部材３が柱材１３へ取り付けられる。【選択図】図５
