In an analysis of a fluid component using a nanomechanical sensor covered with a receptor, the same receptor is caused to express different response characteristics. In a measuring system of analyzing a response when a sample gas and a purge gas are supplied to a nanomechanical sensor while switching the sample gas and the purge gas, a gas (external gas) different from both gases is mixed into a gas channel and supplied to the sensor for measurement. Since a response characteristic of a receptor is modulated by mixing of the external gas, the object described above is achieved.