A pit cover, comprising: a top plate; width direction ribs and length direction ribs formed integrally in a mutually orthogonal lattice of horizontal and vertical straight lines on a reverse surface of the top plate until near the outer periphery of the top plate, so as to be orthogonal to a length direction and a width direction of the top plate, respectively; and a pair of handholds, wherein: a space partitioned by a first rib structure of both end portions of the width direction ribs and of the length direction ribs disposed on the outermost side in the width direction of the pit cover opens towards the end portions in the width direction of the pit cover to form a plurality of first air flow paths communicating between the space and the outside of the pit cover in both end portions in the width direction of the pit cover, and the length direction ribs that cross in a lattice together with the portions other than both end portions of the width direction ribs form the wall portions of a second rib structure that is partitioned into spaces formed in plurality in horizontal and vertical continuation with the reverse surface of the top plate, each of the spaces being surrounded in five directions by respective wall portions and the reverse surface of the top plate, characterized in that the handholds are formed as cut-out portions on both end portions in the width direction of the pit cover at a center portion in the length direction, such as to form a second air flow path directly communicating between the back side of the top plate and the outside of the pit cover, so as to be joined with width direction ribs integrally by handhold ribs in the periphery of the cut-out portions, the first air flow paths and the second air flow path are formed so that both the first air flow paths and the second air flow path face in the same direction in the width direction of the pit cover and the respective first air flow paths sandwich the second airflow path symmetrically to the second air flow path, and the first air flow paths and the second air flow path are formed on the width direction end portions of the pit cover as air flow paths that continuously cross the entire length in the length direction between the length direction end portions of the pit cover. a top plate; width direction ribs and length direction ribs formed integrally in a mutually orthogonal lattice of horizontal and vertical straight lines on a reverse surface of the top plate until near the outer periphery of the top plate, so as to be orthogonal to a length direction and a width direction of the top plate, respectively; and a pair of handholds, wherein: a space partitioned by a first rib structure of both end portions of the width direction ribs and of the length direction ribs disposed on the outermost side in the width direction of the pit cover opens towards the end portions in the width direction of the pit cover to form a plurality of first air flow paths communicating between the space and the outside of the pit cover in both end portions in the width direction of the pit cover, and the length direction ribs that cross in a lattice together with the portions other than both end portions of the width direction ribs form the wall portions of a second rib structure that is partitioned into spaces formed in plurality in horizontal and vertical continuation with the reverse surface of the top plate, each of the spaces being surrounded in five directions by respective wall portions and the reverse surface of the top plate, a space partitioned by a first rib structure of both end portions of the width direction ribs and of the length direction ribs disposed on the outermost side in the width direction of the pit cover opens towards the end portions in the width direction of the pit cover to form a plurality of first air flow paths communicating between the space and the outside of the pit cover in both end portions in the width direction of the pit cover, and the length direction ribs that cross in a lattice together with the portions other than both end portions of the width direction ribs form the wall portions of a second rib structure that is partitioned into spaces formed in plurality in horizontal and vertical continuation with the reverse surface of the top plate, each of the spaces being surrounded in five directions by respective wall portions and the reverse surface of the top plate, characterized in that the handholds are formed as cut-out portions on both end portions in the width direction of the pit cover at a center portion in the length direction, such as to form a second air flow path directly communicating between the back side of the top plate and the outside of the pit cover, so as to be joined with width direction ribs integrally by handhold ribs in the periphery of the cut-out portions, the first air flow paths and the second air flow path are formed so that both the first air flow paths and the second air flow path face in the same direction in the width direction of the pit cover and the respective first air flow paths sandwich the second airflow path symmetrically to the second air flow path, and the first air flow paths and the second air flow path are formed on the width direction end portions of the pit cover as air flow paths that continuously cross the entire length in the length direction between the length direction end portions of the pit cover.