To provide a wind box for a surface combustion burner wherein flames of a uniform size and shape are obtained on a burner surface.

A premix gas supply duct 3 connected parallel to a burner mat 2 fitted on an opening surface side of a box, and a partitioning plate 5 so fitted as to partition an inlet 4 to which the supply duct 3 is connected from the burner mat 2 in the box 1, are provided. The partitioning plate 5 is so fitted that the cross-section area of flow channel of the premix gas is larger on the inlet side while smaller on farthest side of the box 1, and the partitioning plate 5 is provided with small holes which allow the premix gas to pass over the entire surface with constant intervals, while a plurality of baffle plates 7 are fitted in the supply direction of premix gas with intervals.