To prevent peeling of a spray material upon wet spraying the spray material of an MgO material on an operation surface side of a refractory constructed in a tundish.

When performing construction by wet-spraying the spray material 5 of an MgO material on a working surface 4 side of the refractory constructed in the tundish, the spray material 5 having a compressive strength of 3-15 MPa at 110 °C is sprayed in two layers. The thickness of the first layer is 20 mm or more and the total sprayed thickness of the spray material 5 is 30-60 mm. When a crack occurring during curing after the spraying has a width of 10 mm or more, the crack is repaired. The moisture content of the spray material before heating the tundish is 14 mass% or less.