Abstract: Method and apparatus for measuring suspended substance concentrations, wherein the method includes measuring the concentration of suspended substances mixed with a liquid by detecting pressure difference between two points distantly located in the depth direction of the liquid, calculating the average density of the liquid between the two points from the pressure difference, and then calculating difference between the average density and a predetermined reference density of the liquid as an index for determining the suspended substance concentration, whereby real time, continuous measurement and easy maintenance and control with high accuracy and wide measuring range are attained.