Firstly, a shape of a cell as an object of a measurement is modeled, and a complex electric permittivity response when an AC electric field is applied to the cell is obtained through a numerical analysis (Step S1). A numerical calculation is carried out based on that result while values of a membrane capacitance Cm and a cell cytoplasm electric conductivity [kappa]i are changed, thereby calculating a dielectric spectrum (Step S2). The dielectric spectrum thus calculated is revolved to a dielectric relaxation expression, thereby obtaining a rise [Delta][epsilon] in relative electric permittivity and relaxation time [tau] (Step S3). Next, dependency of ([Delta][epsilon], [tau]) on (Cm, [kappa]i) is obtained, thereby creating a regression expression corresponding to the shape of the cell as the object of the measurement (Step S4). A dielectric spectrum of the cell is actually measured, and the resulting values actually measured and the regression expression are compared with each other, thereby obtaining a membrane capacitance Cm, exp and a cell cytoplasm electric conductivity [kappa]i, exp of the cell as the object of the measurement (Step 5).