Abstract: According to one embodiment, a substrate storage container comprises: a container body configured to store a substrate; a lid that closes a rectangular opening of the container body; and an annular gasket located between the container body and the lid. The container body has at least either one of a guide rib or a guide slit in an opening portion around the opening. The lid has at least either one of a guide slit or a guide rib that is engageable with the guide rib or the guide slit of the container body. The guide rib and the guide slit engage each other when the opening is closed with the lid and prevent the lid from tilting at a predetermined tilt angle or more with respect to an opening surface where the opening is formed.