PURPOSE: To simply measure the dynamic surface tension of a liquid sample under the preset conditions near various operating states of the liquid sample by adding a very simple improvement to the conventional vertical plate method.

CONSTITUTION: A solid plate 3 is dipped and suspended in a sample liquid 2 filled in a container 1 while tensile force P is applied upward, the surface tension is measured based on the magnitude of the tensile force P, the weight of the solid plate 3, and the magnitude of the buoyancy applied to the solid plate 3, and a liquid injection port 4 is provided on the container 1. The sample liquid 2 is continuously introduced through the liquid injection port 4, and the surface tension on the surface is measured while the sample liquid 2 is overflowed from the container 1.