The bachelor thesis deals with the study of density of the beech wood substance under pressure. It has a theoretical and practical parts. Theoretical part contains basic information of physical and mechanical properties, also macroscopic and microscopic structure of wood.The practical part deals with the materials, methods of measurment, and at the end deals with the results. The thesis has been devided into two parts: density of beech wood under load at pressure and density of beech wood under load at bending. We measured their weight first (at pressure and bending) in the air and in the water to distinguish between bound and free water. Later on we implemented double weighing method according to Archimedes‘ law. For capturing pressure we have prepared aluminium plate (at pressure) and we have prepared support by aluminium as well. At the end we measured their weight once again. We could easily calculate beech wood densities according to Archimedes’s law. Lastly we deal with results which are accurate and easy to interpret.