PURPOSE: Provided is a method of preparing Laminaria japonica jelly which has abundant dietary fiber and mineral components and shows excellent pharmaceutical efficacies. CONSTITUTION: The method of preparing Laminaria japonica jelly comprises the steps of: adding water to a mixture of agar and refined white sugar, and followed by heating and stirring it; adding sugar syrup thereto to manufacture Brix 75% jelly mixture; dipping Laminaria japonica in 10-70 wt.% of acetic acid solution and adding other ingredients thereto; heating the mixture at 95-105 deg.C; drying and pulverizing the Laminaria japonica; extracting the Laminaria japonica powder with 500cc of water by heating; mixing Laminaria japonica extract, the jelly mixture and sesame seeds; cooling it.