PROBLEM TO BE SOLVED: To provide a trap cage which is designed in consideration of safety when a stopper is released to cause a door to slide down and whose size can be freely changed by using an assembled trap cage to meet requirement of enlargement of the cage, and to provide a lifting door used therefor.SOLUTION: A trap cage 1 is constituted such that a left frame member 2d positioned between an upper frame member 2a and a lower frame member 2b of a ceiling frame 2 is arranged not at an end of the upper frame member 2a and the lower frame member 2b but at a position shifted toward the center from the end. Further, a lifting door 20 is lifted/lowered along a pair of guide rails 9c, 9d. Because a gap of a width w is formed between the opposing faces of the left frame member 2d and the pair of guide rails 9c, 9d, risks of a hand or finger touching the lifting door 20 or being caught between the lifting door 20 and the left frame member 2d are avoided, if the lifting door 20 slides down by self-weight accidentally during trap operation near the frame member.SELECTED DRAWING: Figure 3
