A substrate storage container is provided which can convey, fix and store substrates safely, with threaded members not being loosened by a load applied to a mounting member of the substrate storage container when the container storing substrates is conveyed or when the container is fixed to a substrate processing apparatus and by a heating process at the time of washing and drying of the container. For fastening the mounting member (6), such as a side plate for conveyance, a bottom plate for positioning the container with respect to a substrate processing apparatus, etc., to the substrate storage container including a container body (1) and a lid (2) by threaded members (3), a locking means for preventing loosening of the threaded members (3) is interposed between engagement surfaces of each threaded member (3) and the mounting member (6).