A substrate storage container which includes: a front-opening box type container body for storing a multiple number of substrates in alignment therein; a door for opening and closing the open front of the container body in a sealing manner; and inner-pressure adjustment devices attached to the mounting ports in the container body and the door for adjusting the pressure inside the container body closed with the door. The inner-pressure adjustment device is configured of an elastic attachment cylinder, a filter support structure fitted into, and protected by, the attachment cylinder and a multiple number of filters held inside the filter support structure. Since the inner-pressure adjustment device can be set by mounting an attachment cylinder of a simple structure by use of elastic deformation to the attachment hole, which is provided for the container body and/or the door, there is no need of forming screw holes which need time and effort.