The present invention addresses the problem of providing a chelate color former which can measure the concentration of iron with high sensitivity and with low blank values when measuring the concentration of iron, and an iron concentration measurement method and kit that use this chelate color former. The present invention relates to: a compound represented by following formula [1] or a salt thereof wherein, R1 and R2 each independently represent —SO3H or —CO2H; an iron concentration measurement method in which the compound is used as a chelate color former, the compound is brought into contact with iron in a sample, and the concentration of iron in the sample is measured on the basis of the degree of resulting color development; and a kit to be used therein.