PURPOSE: To improve the apparent access processing speed of the magnetic disk storage device in the view from a host device side.

CONSTITUTION: This magnetic disk storage device is equipped with plural data buffers 18a and 18b for storing data on an address-specified access request and an access result, plural disk enclosure parts 12a and 12b which execute access requests stored in the buffers that they are connected, an access request distribution part 17 which distributes and writes address-specified access requests inputted in order from an external host device 15 through a data input/output part 16 to the data buffers 18a and 18b according to a specific address distribution rule and sends out data on access results read out of the disk enclosure parts 12a and 12b to the data buffers 18a and 18b to the data input/output part 16, and a case 11 which contains the data buffers 18a and 18b, disk enclosure parts 12a and 12b, data input/output part 16, and access request distribution 17 in common.