PROBLEM TO BE SOLVED: To provide an analysis method capable of stably measuring a metal element concentration or the like with desired accuracy and low environmental load without unnecessarily high cost in measuring the concentration of each metal element and a lithium/metal ratio in a sample such as a lithium secondary battery positive electrode material.SOLUTION: A method of analyzing a concentration of a metal element in a sample solution using an inductive coupling plasma emission spectrophotometer to which an internal standard correction method using yttrium or copper as an internal standard element is applied and which uses a plasma excitation temperature equal to or higher than 4900K, comprises: determining a relational expression between the measuring accuracy for a lithium/metal ratio and a temperature control width of refrigerant for a detection unit of the spectrophotometer by measurement using the spectrophotometer; specifying the refrigerant temperature control width necessary to satisfy required
