A substrate storage container includes a container body configured to store a substrate, a lid that closes the opening of the container body, a retainer that is attached to the lid, and a substrate support portion formed in the retainer. The substrate support portion has an arc shape in a cross-sectional view from the top-to-bottom direction perpendicular to the closing direction of the lid. The substrate support portion includes a pair of left and right substrate support portions configured to hold the substrate together with the container body to retain the substrate.