Reduction of the initial investment cost of a user of a storage system can be realized, and the user of the storage system can easily perform timely addition for a short time. In a preferred embodiment, a method for renting and charging the storage system includes the steps of: reading a used volume from a use management table held in the storage system; and sending the read used volume from the storage system to a charging system. Preferably, the storage system has means for allowing an owner to grasp that a user starts using the storage system, wherein the owner rents to the user a storage system having a disk volume, a cache volume, and other components more than the user's increase intension, charges for a used volume of the user for a fixed period, and reviews the added volume and the charged cost on the fixed period basis.