To provide a groove opening and closing device by which a person or a truck is enalbed to go in and out safely and a closing structure of an entrance opening using a door main body having the device.

This device includes an elevating plate 16 disposed in a groove part 2 formed below the floor F to insert the lower end of the sliding type door main body 3 and formed in the opening and closing direction of the door main body 3, and driving devices 17, 18 for driving the elevating plate 16 to be elevated. The elevating plate 16 is lowered when an entrance opening G is closed by the door main body 3, and is raised to make the upper surface flush with the floor F when the entrance opening G is opened by the door main body 3.