When we measure expansive pressure of expansive demolition agent, “outer pipe method” has been generally adopted, which is calculated by the strain of strain gauges put on the outersurface of steel pipe. But in this method, steel pipes are not reusable because hardened materials in steel pipes are too hard to remove. Authors discovered that expansive pressure of expansive demolition agent is transmitted in a manner similar to that of fluid. And utilizing this character, authors developed new measuring method of expansive pressure using pressure transducer. This paper examines the accuracy of measuring value comparing the conventional outer pipe method. Test result are as follows: The standard deviation of expansive pressure using this method is 40% less than that of using outer pipe method. Besides, steel pipes are reusable due to the taper rod set inside the steel pipe when using this method.