A method for quantitative determination of nickel and/or copper, by which an ultratrace amount of nickel and/or copper contained in a liquid sample can be easily and simply determined in situ; and apparatus to be used in the method. The method comprises a step of adding a complex-forming agent capable of forming a complex with nickel and copper to a liquid sample containing nickel and/or copper in unknown concentrations to form colored fine particles of a nickel complex and/or a copper complex and a step of determining the quantities of nickel and/or copper on the basis of the colored fine particles.