In a measurement method, light inputs with the same center wavelength and different properties are performed on a light transmission medium, and a measured value of an intensity spectrum of each of light outputs is acquired. An error between the measured value and an estimated value of the intensity spectrum calculated based on a theoretical relation between an intensity spectrum and a phase spectrum of each of the light inputs, a nonlinear coefficient and a wavelength dispersion value of the light transmission medium, and the intensity spectrum of each of the light outputs is calculated while changing the nonlinear coefficient and the wavelength dispersion value. Further, the nonlinear coefficient and the wavelength dispersion value are determined based on a difference, in a relation between the nonlinear coefficient and the wavelength dispersion value and the error, between the light inputs.