A cooling apparatus comprising a liquid immersion cooling apparatus filled with liquid coolant, the cooling apparatus including an electronic device (100; 300) that is immersed in the liquid coolant filled in the liquid immersion cooling apparatus , and directly cooled, the electronic device being configured to be housed in a housing part of the liquid immersion cooling apparatus, the electronic device comprising: a base board (110; 310); a plurality of storage substrates to be arranged on at least one surface of the base board (110; 310); a backplane including a plurality of connectors for electric connection of the respective storage substrates , the backplane being mounted orthogonally onto the at least one surface of the base board (110; 310); and a plurality of flash storage units mounted on the respective storage substrates , wherein: the backplane includes a combination of a plurality of backplane units arranged in a length direction of the base board (110; 310) to form a single substrate, each of the backplane units including a signal connector and a power connector , the signal connector and the power connector being disposed separately for each of the backplane units , and the flash storage units each having a rectangular shape are arranged on a surface parallel to at least one surface of each of the storage substrates so as to be adjacent one another in a width or a length direction, or in both the width and the length directions of the rectangular-shaped flash storage unit . a base board (110; 310); a plurality of storage substrates to be arranged on at least one surface of the base board (110; 310); a backplane including a plurality of connectors for electric connection of the respective storage substrates , the backplane being mounted orthogonally onto the at least one surface of the base board (110; 310); and a plurality of flash storage units mounted on the respective storage substrates , wherein: the backplane includes a combination of a plurality of backplane units arranged in a length direction of the base board (110; 310) to form a single substrate, each of the backplane units including a signal connector and a power connector , the signal connector and the power connector being disposed separately for each of the backplane units , and the flash storage units each having a rectangular shape are arranged on a surface parallel to at least one surface of each of the storage substrates so as to be adjacent one another in a width or a length direction, or in both the width and the length directions of the rectangular-shaped flash storage unit . the backplane includes a combination of a plurality of backplane units arranged in a length direction of the base board (110; 310) to form a single substrate, each of the backplane units including a signal connector and a power connector , the signal connector and the power connector being disposed separately for each of the backplane units , and the flash storage units each having a rectangular shape are arranged on a surface parallel to at least one surface of each of the storage substrates so as to be adjacent one another in a width or a length direction, or in both the width and the length directions of the rectangular-shaped flash storage unit . <EOS>