To provide a method for controlling seedling blast, by which the blast in a seedling-raising period can effectively be controlled with a small application amount of a fungicidally active compound.

Provided is the method for controlling the seedling blast, characterized by mixing a composition containing 50 to 80 wt.% of a benzimidazole skeleton-having compound with the bed soil and/or cover soil of a rice seedling box in a composition amount of 0.1 to 2 g per rice seedling box (30 cm60 cm3 cm) without diluting with water. The benzimidazole skeleton-having compound is preferably one or more compounds selected from benomyl, carbendazim, thiabendazole, and thiophanate-methyl. The formulation of the composition is preferably one of water-dispersible powder, powder, fine granules, and granules.