To provide an antifreezing cover for a perforated plate for a drainage effectively preventing the freezing of the perforated plate and ensuring a proper drainage function at all times.

The antifreezing cover prevents the freezing of the perforated plate for the drainage with a plurality of perforated-plate holes. A top plate capable of covering the perforated plate is installed on a frame body laid along the inside of the peripheral section of the perforated plate, and an air layer filled with the heat of the earth is formed inside the top plate. The frame body is arranged on a lattice forming joint holes so as not to close the joint holes positioned at at least the peripheral section of the perforated plate, and water can be drained through the joint holes. A plurality of fixing legs engaged with the joint holes of the peripheral section of the perforated plate are projected at the proper places of the peripheral section of the top plate.