Conventionally, only a pair of electrodes is provided and nanopores arranged in parallel are connected by an electrolyte solution, and therefore a change in an ion current to be measured is a sum of changes in ion currents generated in the respective nanopores. The invention includes: a first solution chamber including a plurality of first electrodes; a second solution chamber including a second electrode which is a counter electrode of the first electrodes; a membrane provided between the first solution chamber and the second solution chamber, the membrane having a plurality of small holes; a measuring unit for applying a voltage between the first electrodes and the second electrode and measuring a current flowing between the first electrodes and the second electrode via the small holes; and an insulating structure forming unit for forming, in the first solution chamber, an insulating structure for insulating the first electrodes in a state in which a conductive liquid is filled between the small holes and the first electrodes and achieves parallel measurement of ion currents by using nanopores.