An object of the present invention is to provide an optical measurement apparatus equipped with an ion-exchange resin for pretreating a sample, thereby enabling the concentration of component in the sample to be measured with higher accuracy. The optical measurement apparatus of the present invention includes, in addition to the ion-exchange resin, an optical measurement section for measuring, based on the optical characteristics of the component, the concentration of the component in the sample after the sample is passed through the ion-exchange resin.