MicroRNA, a short-length RNA known as a biomarker of cancers, was detected by magnet-attached spiral channel and electrical measurement. A designed oligo-DNA bound with magnetic bead was entrapped in spiral channel by magnetic field, and hybridized with microRNA. Thereafter, liposome were exported from the spiral channel by duplex-specific nuclease, and applied to electrical measurement. Finally, ionic current signals were observed specifically when the target microRNA was applied. Whereas, when a mixture of over 106 different mock microRNAs were applied, no signals were observed. This indicates a noise-free, high selectivity was achieved in the presented device.