Icheon Seolbong fortress is located in Saum-dong, Icheon, Gyeonggi-do Province that its date is founded as 4th century of Bakjae dynasty after excavation by Dankook university museum. Excavated artifacts show various kinds such as earthenwares, ceramics, metal artifacts and so on. Especially many iron artifacts were founded in where Bakjae earthenwares were found that it indicates iron artifacts were manufactured in Bakjae Dynasty. From 6 iron sickles, called Beollat and Millet, samples were taken to examine mircostructures and from the results used iron material, shape-forging, steel-making process, heat treatment were investigated. From this late 4th century Bakjae dynasty iron manufacture profess was established. From the result, different treatment were used in different area of the sickles according to the its use. Beollats were quenched in blade and it was used for special purpose that require Intensity. Millats did not have special treatment that it was used to cut rice plant and plant. Used material was steel, steel was previously made by certain steel-making process. It is formed to produce iron ware and the area where intensity is required heat treatment was employed to make it strong. From the investigation it is derived that iron ware manufacture process in Bakjae dynasty is steel makingshape-forgingand heat treatment.