A paper sheet storing unit comprising: a chassis; a deposit unit configured to take a paper sheet into the paper sheet storing unit; and a storing unit configured such that a paper sheet storing bag is detachably attachable to the storing unit for storing the paper sheet taken into the paper sheet storing unit by the deposit unit through an upper opening of the paper sheet storing bag, the paper sheet storing bag including a retained member having an opening provided in a hook portion of the retained member, wherein the storing unit includes a first retention member and a second retention member for retaining the paper sheet storing bag, while the upper opening of the paper sheet storing bag is opened, the first retention member and the second retention member are separately placed in an identical horizontal plane along a depth direction of the chassis and are configured to retain the paper sheet storing bag between the first retention member and the second retention member, the first retention member and the second retention member retaining the paper sheet storing bag are configured to be integrally drawable to an outside from the paper sheet storing unit along a depth direction of the chassis that is orthogonal to the width direction of the chassis, and the first retention member is configured to be movable toward the second retention member along the width direction of the chassis, and the upper opening of the paper sheet storing bag is configured to be sealed when the first retention member moves toward and abuts on the second retention member, wherein the first retention member and the second retention member further include a protrusion member configured to protrude through the opening of the retained member of the paper sheet storing bag being attachable to the storing unit so that the protrusion member is configured to fix the retained member of the paper sheet storage bag, the protrusion member is configured to be retractable into the first retention member and the second retention member, wherein a pin accommodation member is provided in each of the first retention member and the second retention member, the protrusion member is accommodated in each pin accommodation member and a hook section is provided in the pin accommodation member, a bag unfixing lever is provided in each of the first retention member and the second retention member, wherein the bag unfixing lever is configured to be manually pressed and when the bag unfixing lever is manually pressed downward, it causes the hook section to move downward and the protrusion member retracts into the first retention member and the second retention member, causing the protrusion member to fall out of the opening of the paper sheet storing bag and the paper sheet storing bag is releasable from the first retention member and the second retention member. a chassis; a deposit unit configured to take a paper sheet into the paper sheet storing unit; and a storing unit configured such that a paper sheet storing bag is detachably attachable to the storing unit for storing the paper sheet taken into the paper sheet storing unit by the deposit unit through an upper opening of the paper sheet storing bag, the paper sheet storing bag including a retained member having an opening provided in a hook portion of the retained member, wherein the storing unit includes a first retention member and a second retention member for retaining the paper sheet storing bag, while the upper opening of the paper sheet storing bag is opened, the first retention member and the second retention member are separately placed in an identical horizontal plane along a depth direction of the chassis and are configured to retain the paper sheet storing bag between the first retention member and the second retention member, the first retention member and the second retention member retaining the paper sheet storing bag are configured to be integrally drawable to an outside from the paper sheet storing unit along a depth direction of the chassis that is orthogonal to the width direction of the chassis, and the first retention member is configured to be movable toward the second retention member along the width direction of the chassis, and the upper opening of the paper sheet storing bag is configured to be sealed when the first retention member moves toward and abuts on the second retention member, wherein the first retention member and the second retention member further include a protrusion member configured to protrude through the opening of the retained member of the paper sheet storing bag being attachable to the storing unit so that the protrusion member is configured to fix the retained member of the paper sheet storage bag, the protrusion member is configured to be retractable into the first retention member and the second retention member, wherein a pin accommodation member is provided in each of the first retention member and the second retention member, the protrusion member is accommodated in each pin accommodation member and a hook section is provided in the pin accommodation member, a bag unfixing lever is provided in each of the first retention member and the second retention member, wherein the bag unfixing lever is configured to be manually pressed and when the bag unfixing lever is manually pressed downward, it causes the hook section to move downward and the protrusion member retracts into the first retention member and the second retention member, causing the protrusion member to fall out of the opening of the paper sheet storing bag and the paper sheet storing bag is releasable from the first retention member and the second retention member.