A planar patch clamp device comprising: an electrical insulating substrate having a first surface having a cell arrangement region and a second surface of the opposite surface and having a through hole in the cell arrangement region which does not pass cells, but pass liquid; a first reservoir provided at the first surface side of the electrical insulating substrate to be able to communicate with the through hole and hold a first conductive liquid; a first electrode part arranged to be able to be electrically conductive with the first reservoir through the first conductive liquid; a second reservoir provided at the second surface side of the electrical insulating substrate to be able to communicate with the through hole and hold a second conductive liquid; a second electrode part arranged to be able to be electrically conductive with the second reservoir through the second conductive liquid; a supply path connected to the second reservoir and supplying the second conductive liquid to the second reservoir; a discharge path connected to the second reservoir and discharging the second conductive liquid from the second reservoir; and a valve provided in the supply path and/or discharge path, able to allow or stop the flow of the second conductive liquid, and also able to allow or stop electrical conduction between the second reservoir and the second electrode part, wherein the electrical insulating substrate has a plurality of cell arrangement regions and corresponding through holes and is provided with a plurality of second reservoirs corresponding to the plurality of cell arrangement regions; characterized in that the supply path has a main supply path and a plurality of branch supply paths respectively branched from the main supply path and connected to the plurality of second reservoirs; the discharge path has a plurality of branch discharge paths respectively connected to the plurality of the second reservoirs and a main discharge path where the plurality of branch discharge paths merge; the second electrode part is provided at the main supply path and/or main discharge path; and a valve is provided at each branch supply path and/or each branch discharge path, able to allow or stop the flow of the second conductive liquid, and also able to allow or stop electrical conduction between the second reservoirs and the second electrode part. an electrical insulating substrate having a first surface having a cell arrangement region and a second surface of the opposite surface and having a through hole in the cell arrangement region which does not pass cells, but pass liquid; a first reservoir provided at the first surface side of the electrical insulating substrate to be able to communicate with the through hole and hold a first conductive liquid; a first electrode part arranged to be able to be electrically conductive with the first reservoir through the first conductive liquid; a second reservoir provided at the second surface side of the electrical insulating substrate to be able to communicate with the through hole and hold a second conductive liquid; a second electrode part arranged to be able to be electrically conductive with the second reservoir through the second conductive liquid; a supply path connected to the second reservoir and supplying the second conductive liquid to the second reservoir; a discharge path connected to the second reservoir and discharging the second conductive liquid from the second reservoir; and a valve provided in the supply path and/or discharge path, able to allow or stop the flow of the second conductive liquid, and also able to allow or stop electrical conduction between the second reservoir and the second electrode part, wherein the electrical insulating substrate has a plurality of cell arrangement regions and corresponding through holes and is provided with a plurality of second reservoirs corresponding to the plurality of cell arrangement regions; characterized in that the supply path has a main supply path and a plurality of branch supply paths respectively branched from the main supply path and connected to the plurality of second reservoirs; the discharge path has a plurality of branch discharge paths respectively connected to the plurality of the second reservoirs and a main discharge path where the plurality of branch discharge paths merge; the second electrode part is provided at the main supply path and/or main discharge path; and a valve is provided at each branch supply path and/or each branch discharge path, able to allow or stop the flow of the second conductive liquid, and also able to allow or stop electrical conduction between the second reservoirs and the second electrode part.