Solid-state electrochemical sensors are developing as a new platform for liquid biopsy, combining detection and analysis of nucleic acids with isothermal nucleic acid amplification reactions. For the detection of small nucleic acids such as cfDNA, ctDNA and miRNA in liquid biopsy, further development of highly sensitive and precise devices is required to transcend the barrier of classical detection technology. Electrochemical sensors based on engineering approaches are advantageous for miniaturization of systems and convenience of diagnosis, and the analysis of data obtained with these sensors dovetails with transition to an information society. This review briefly surveys the current development of electrochemical sensors combined with isothermal amplification for nucleic acid detection and predicts the future direction of research.