There are provided a method and apparatus for detecting nucleic acid using bead and nanopore, and more specifically, a method and apparatus capable of detecting nucleic acid fragments of 70 bps to 300 bps in length by a nanopore detection unit with nanopores of 20 to 120 nm in diameter by attaching a bead to a nucleic acid probe and then detecting the bead attached to nucleic acid not nucleic acid itself. Accordingly, the present invention can detect the nucleic acid fragments using the nanopore detection unit with nanopores of 20 to 120 nm in diameter, even in case where Polymerase Chain Reaction (PCR) products are given as the sample, particularly the PCR products are the nucleic acid fragments of 70 to 300 bps in length.