To solve the problem of requiring much labor for work, for requiring to measure a pole diameter for sure gripping, for requiring to make an adjustment in advance in response to the pole diameter such as an electric pole, because many fatal and injury accidents takes place conventionally by overturning due to unstability when stepping up the electric pole by setting up a ladder and a stepladder.

This ladder overturning preventive device has an arm part composed of a pair of arms mutually energized in the closing direction for nipping an object, and a fixing part for fixing the arm part to the ladder.