A method for measuring cancer related substances including cancer cell-derived free DNA by Raman spectroscopy, involving steps for preparing a biochip having a meso-crystal region of silver oxides containing a silver peroxide, adding a blood serum or a biological sample solution dropwise onto the meso-crystal region of said biochip, selectively trapping the cancer-related substances having a positive charge in the sample, irradiating the trapped cancer-related substance with an exciting laser light and detecting a surface enhanced Raman scattering therefrom, wherein cancer diseases are evaluated on the basis of the intensity of the Surface Enhance Raman Scattering (SERS). In the carbon-specific D band and G band in the Raman scattering spectrum, a characteristic peak spectrum of the cancer-related substance can be detected in the proximity of the methyl group characteristic of 2900 cm−1.