Cancer precision medicine has become widespread in the world. In Japan, genomic profiling tumor tissues using next generation sequencing(NGS)has been reimbursed to enable simultaneous measurement of multiple biomarkers and genomic abnormalities in clinical practice. However, NGS analysis of tumor tissue has several problems, including long turnaround time, and difficulty in capturing heterogeneity and longitudinal genotyping. Liquid biopsy, an advanced technique that has been developed in recent years, can assess the status of tumors using samples of body fluids, such as blood and urine, without the use of tumor tissue. In particular, circulating tumor DNA(ctDNA), which is released from tumor cells into the blood by apoptosis and necrosis, can be used to select molecularly targeted therapies, monitor therapeutic efficacy, and determine risk of recurrence and select for adjuvant chemotherapy by assessment of minimal residual disease(MRD). In this review, we outline the usefulness, disadvantages and future perspectives of ctDNA analysis.