In recent years, various isothermal amplification techniques have been developed as alternatives to polymerase chain reaction (PCR). The integration of isothermal amplification with electrical or electrochemical devices has enabled high-throughput nucleic acid-based assays with high sensitivity. We performed solid-phase rolling circle amplification (RCA) on the surface of a Au electrode, and detected RCA products in situ using chronocoulometry (CC) with [Ru (NH3)6]3+as the signaling molecule. Detection sensitivity for DNA and a microRNA (miR-143) was 100 fM and 1 pM, respectively. Furthermore, we conducted potentiometric DNA detection using an ethidium ion (Et+)-selective electrode (Et+ISE) for real-time monitoring of isothermal DNA amplification by primer-generation RCA (PG-RCA). The Et+ISE potential enabled real-time monitoring of the PG-RCA reaction in the range of 10 nM–1 μM of initial target DNA. Devices based on these electrochemical techniques represent a new strategy for replacing conventional PCR for on-site detection of nucleic acids of viruses or microorganisms.