A sensitive density meter for measuring the density of small amounts of solid, solution, or dispersed materials, e.g., biological systems in the liquid environment, is presented. The chamber for the measured sample is in the lower part of a glass buoy. It is closed by the glass stopper containing the permanent magnet. The buoy is immersed in the carrying liquid with the known density and is balanced by the magnetic force. The device enables the measurement at constant temperature as well as in the temperature scanning regime. The accuracy of measuring the liquid density is 1 mg/lin a 1.5 ml chamber; the sensitivity of measuring the temperature is 1 mK. The volume of solids or dispersed systems of known weight is measured with an accuracy of 1.5 nl.