The present inventors analyzed genes involved in plant disease resistance. As a result, they discovered the transcription factor gene OsWRKY45, which is induced in leaf blades of rice plants by activating the systemic acquired resistance (SAR) that plants inherently have, i.e., by treating rice plants with benzothiadiazole (hereafter may be abbreviated as BTH), which is an agent thought to induce disease resistance in plants. It was further discovered that rice blast disease resistance and rice bacterial leaf blight resistance were markedly improved by reintroducing the gene into rice plants and constitutively expressing it.