A method of measuring a state of concrete includes emitting an irradiation light to the concrete, the irradiation light including a wavelength range of near infrared light related to concrete measurement; and receiving a reflection light of the irradiation light P reflected on the concrete. 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, are determined, and a degree of neutralization of the concrete caused by calcium hydroxide and a concentration of chloride ion is estimated.