Lid unit for a thin-plate supporting container

The attaching-and-detaching operation of a lid unit is automated using an existing attaching-and-detaching device. A lid unit (14) for closing a container body (12) of a thin-plate supporting container for use in storing semiconductor wafers (49) therein is provided. A simplified attaching-and-detaching mechanism (26) allows the lid unit (14) to be attached and detached by easy locking and unlocking with respect to the container body (12). The simplified attaching-and-detaching mechanism (26) includes a locking member (42) engageable with a second receiving device (24) of the container body (12), and a guiding member (43) disposed at the extremity of the locking member (42), which guiding member (43) reaches the second receiving device (24) and guides the locking member (42) into the second receiving device (24) in a state in which the main body (30) fits lightly in the container body (12). The guiding member (43) includes a reaching portion (43A) that first reaches the second receiving device (24), and a guiding portion (43B) that guides the locking member (42) to the second receiving device (24).