A biomolecule measuring device includes a first liquid tank and a second liquid tank which are filled with an electrolytic solution, a nanopore device that supports a thin film having a nanopore and is provided between the first liquid tank and the second liquid tank so as to communicate between the first liquid, tank and the second liquid tank through the nanopores, and an immobilizing member that is disposed in the first liquid tank, has a size larger than that of the thin film, and to which the biomolecules are immobilized, in which at least, one of the nanopore device and the immobilizing member has a groove structure.