A measurement method includes a measurement step of measuring a first single value and a second signal value, the first signal value being based on a reaction between a first reacting substance and the sample, the second signal value being based on a reaction between a second reacting substance and the sample, the first reacting substance having a higher reactivity to a second detection target than to a first detection target, the second reacting substance having a higher reactivity to the first detection target than to the second detection target.