The present invention relates to a method for measuring the concentration of a particular component in a blood sample containing blood cells based on a variable correlated with the concentration of the particular component. In the present invention, a concentration (S) in blood plasma obtained by removing blood cell components from the blood sample, a concentration (DI) in the blood sample computed by a differential method and a concentration (EP) in the blood sample computed by an equilibrium point method are expressed by a relational expression which is unrelated to the proportion of the blood cell components in the blood sample, and the concentration of the particular component is computed by using the relational expression.