NOVELTY - The apparatus has a connection tool (26) for electrically connecting the test tank (13) in which tested-substance (W) is accommodated. A charging/discharging power supply (8) is provided out of test tank. A heat insulating material (30) is arranged among internal and external wall boards (29a,29b) that close the opening (33) formed in a heat insulation wall portion which section-forms test tank from both sides. The mounting holes (28) are formed in the internal and external wall board and are respectively mounted with the connection tool, so that both the wall boards are penetrated.    USE - Apparatus for testing charging/discharging of double layer capacitor and secondary battery such as nickel cadmium battery, lithium ion battery and nickel-hydrogen battery used in electronic device and electric vehicle.    ADVANTAGE - The mounting holes are formed in the internal and external wall board and are respectively mounted with the connection tool in order to penetrate wall boards, so that the tested-substance and power supply can be electrically connected without the need of power supply connecting cable and hence the improvement in space efficiency and reduction in troublesome power supply connection can be achieved. The heat insulating material is arranged among internal and external wall boards that close the opening formed in a heat insulation wall portion which section-forms the test tank from the both sides, so that the need of manufacturing whole test tank according to specification is eliminated and hence the manufacturing process is simplified and the production cost can be reduced.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for manufacturing method of charging/discharging testing apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of test tank. (Drawing includes non-English language text)    Charging/discharging power supply (8)    Test tank (13)    Connection tool (26)    Mounting holes (28)    Internal wall board (29a)    External wall board (29b)    Heat insulating material (30)    Opening (33)    Tested-substance (W)