An ant-falling device includes a shell, a first axle and a second axle supported therein, a buffer unit coupled at the first axle, and a reel spring for retracting the buffer unit. The buffer unit includes a rope reel and a driven gear. The second axle includes a driving gear, a first buckling member, and a handle that controls the driving gear to engage with the driven gear for retracting a rope via the rope reel. The shell includes a button, having a second buckling member, movably mounted thereon and being pushed by a spring. When the driving gear is engaged with the driven gear, the button is actuated to couple the second buckling member with the first buckling member to enable the rope being smoothly retracted. As the button is pressed, the first buckling member is released to disengage the driving gear with the driven gear.