To provide a method of measuring a state of concrete capable of easily determining or measuring deterioration of the concrete without using a spectroscopy while maintaining the estimation accuracy. The method of the present disclosure emits an irradiation light to the concrete, the irradiation light including a wavelength range of near infrared light related to concrete measurement; and receives a reflection light of the irradiation light P reflected on the concrete. The method determines at least five wavelengths λ1 to λ5, λ6 to λ10, different from each other by PLS regression analysis within a wavelength range of 900 nm to 2500 nm of absorption spectrum, and estimates a degree of neutralization of the concrete caused by calcium hydroxide and a concentration of chloride ion.