PURPOSE: To build a drop tower relatively economically in a place convenient for traffic by providing a drop hole having a free capsule dropping section in the upper part and a control section in the lower part perpendicularly to the ground in a high-rise building.

CONSTITUTION: A drop hole 2 is provided perpendicularly continuously to the ground 6 in a part of a high-rise building 1. By dropping freely a capsule 3 through a free drop part 2a of the upper portion of the drop hole 2, slight gravity for an experimental sample in the capsule 3 is generated. A control section 2b incorporating a braking device 4 therein is provided in the lower part of the drop hole 2 to decelerate the dropping speed of the freely dropping capsule 3 and stop it. Also, a capsule setting chamber 5 for setting the capsule 3 to the drop hole 2 is provided on the upper side of the drop hole 2. The ratio of the free drop section 2a to the braking section 2b in the length is about 75:25. For example, assuming the height of the building 1 is about 200m, the height of the drop section 2a is about 148m and slight gravity time generated in the sample is about 5.5 seconds, so that the drop hole 2 can be effectively built in the building 1.