PURPOSE: Provided is an agent for preventing the approach of snail to C. unshiu Marcow by pulverizing leaves, stems and roots of Nicotiana tabacum to use nicotine thereof. Therefore, the agent prevents the approach of snail to C. unshiu Marcow environmentally friendly by no using chemicals. CONSTITUTION: The agent for preventing the approach of snail to C. unshiu Marcow is manufactured by: pulverizing leaves, stems and roots of Nicotiana tabacum; dissolving 50g of glycerine and 50g of alum in 300g of water; mixing 1000g of the pulverized leaves, stems and roots of Nicotiana tabacum in the solution; and steaming the mixture and drying it in the shade.