To provide a joint construction for covering lids capable of definitely stopping the inflow of rain water or chemical liquid through a gap between covering lids and also making the attach and detach of the lids, easier.

At the right and left side edges of the first covering lid 3, the first projected portion 6 protruded upward is provided over the whole length in the back and forth direction; at the right and left side edge of the second covering lid 4, a second projected portion 7 protruded downward is provided, the second projected portion 7 is arranged on the first covering lid 3 at the inner side of the first projected portion 6, the inner side portion of the first projected portion 6 and the inner side portion of the second projected portion 7 are arranged oppositely to each other, and the first covering lid 3 is functioned as a drainage gutter in the back and forth direction.