A lid for an underground structure, comprising a lid body, and a receiving frame for supporting the lid body at an inner peripheral portion thereof in an openable/closable manner, characterized in that the inner peripheral portion of the receiving frame comprises: a receiving-frame first surface part which is formed to have a gentle gradient forming an angle ranging from 25° to 45° with reference to a vertical line by reducing a diameter toward a downward direction of the receiving frame, and a receiving-frame second surface part which is formed below the receiving-frame first surface part and with a steeper gradient than that of the receiving-frame first surface part by reducing a diameter toward the downward direction of the receiving frame, and a receiving-frame third surface part which is formed below the receiving-frame second surface part and with a gradient different from that of the receiving-frame second surface part by reducing a diameter toward the downward direction of the receiving frame, and an outer peripheral portion of the lid body comprises: a lid first surface part which is formed to have a gentle gradient forming an angle ranging from 25° to 45° with reference to a vertical line_by reducing a diameter toward a downward direction of the lid body, a lid second surface part which is formed below the lid first surface part and vertically toward the downward direction of the lid body, or with a steeper gradient than that of the receiving-frame second surface part by reducing a diameter toward the downward direction of the lid body, and a lid third surface part which is formed below the lid second surface part and with a gradient different from that of the lid second surface part by reducing a diameter toward the downward direction of the lid body, and w herein in a closed-lid state of the lid body, the lid first surface part is supported by the receiving frame first surface part, and at least either one of the lid second surface part and the lid third surface part, and at least either one of the receiving-frame second surface part and the receiving-frame third surface part are pressed against each other by a pressing force caused by elastic deformation of at least either one of the outer peripheral portion of the lid body and the inner peripheral portion of the receiving frame. a receiving-frame first surface part which is formed to have a gentle gradient forming an angle ranging from 25° to 45° with reference to a vertical line by reducing a diameter toward a downward direction of the receiving frame, and a receiving-frame second surface part which is formed below the receiving-frame first surface part and with a steeper gradient than that of the receiving-frame first surface part by reducing a diameter toward the downward direction of the receiving frame, and a receiving-frame third surface part which is formed below the receiving-frame second surface part and with a gradient different from that of the receiving-frame second surface part by reducing a diameter toward the downward direction of the receiving frame, and an outer peripheral portion of the lid body comprises: a lid first surface part which is formed to have a gentle gradient forming an angle ranging from 25° to 45° with reference to a vertical line_by reducing a diameter toward a downward direction of the lid body, a lid second surface part which is formed below the lid first surface part and vertically toward the downward direction of the lid body, or with a steeper gradient than that of the receiving-frame second surface part by reducing a diameter toward the downward direction of the lid body, and a lid third surface part which is formed below the lid second surface part and with a gradient different from that of the lid second surface part by reducing a diameter toward the downward direction of the lid body, and w herein in a closed-lid state of the lid body, the lid first surface part is supported by the receiving frame first surface part, and at least either one of the lid second surface part and the lid third surface part, and at least either one of the receiving-frame second surface part and the receiving-frame third surface part are pressed against each other by a pressing force caused by elastic deformation of at least either one of the outer peripheral portion of the lid body and the inner peripheral portion of the receiving frame. a lid first surface part which is formed to have a gentle gradient forming an angle ranging from 25° to 45° with reference to a vertical line_by reducing a diameter toward a downward direction of the lid body, a lid second surface part which is formed below the lid first surface part and vertically toward the downward direction of the lid body, or with a steeper gradient than that of the receiving-frame second surface part by reducing a diameter toward the downward direction of the lid body, and a lid third surface part which is formed below the lid second surface part and with a gradient different from that of the lid second surface part by reducing a diameter toward the downward direction of the lid body, and w herein in a closed-lid state of the lid body, the lid first surface part is supported by the receiving frame first surface part, and at least either one of the lid second surface part and the lid third surface part, and at least either one of the receiving-frame second surface part and the receiving-frame third surface part are pressed against each other by a pressing force caused by elastic deformation of at least either one of the outer peripheral portion of the lid body and the inner peripheral portion of the receiving frame.