Abstract: The present invention relates to an insulin precursor purifying method for improving the production yield of an insulin precursor by adjusting the pHs of a first buffer solution for equilibrating an ion exchange resin and a second buffer solution for eluting an insulin precursor bound to the ion exchange resins. The insulin precursor purifying method according to the present invention is a high-purity and high-yield insulin precursor purifying method for reinforcing by mean of suitable pH combination of buffer solutions, the binding force of an insulin precursor to ion exchange resins and enabling the insulin precursor to be effectively eluted thereafter, and is very useful in high-yield insulin production through enzymatic conversion after a purification process.