To solve the problem wherein when a container containing a reagent is firmly fixed, falling can be prevented, but it is inconvenient to handle because some reagents are originally very poisonous and have high inflammability like concentrated sulphuric acid and the like so that it is dangerous when the container falls due to careless work or quaking due to an earthquake to cause flow-out of the reagent.

This container falling preventing instrument includes: a body 3 formed like a sheet opposite to the bottom 9 of the container 7 containing a reagent or the like; a surface side adhesive layer 15 formed on the surface side of the body 3; and a backside sticky layer 17 formed on the backside of the body 3. The instrument is formed to be different between the adhesive strength to the container 7 and the adhesive strength to a stand 31 for placing the container 7. In the case of the mounting type where the adhesive strength to the container 7 is larger than the adhesive strength to the stand 31, when the instrument is stuck to the container 7 and placed on the stand 31, the container 7 is fixed to the stand 31 through the falling preventing instrument 1 so that when the container 7 is lifted by hand, the falling preventing instrument 1 is separated along with the container 7 from the stand 31. When it is placed again on the stand 31, it is fixed to the stand. An adsorbing layer is preferably formed in place of the adhesive layer.