For this study, we examined the male costumes in the United Silla Era through Stone guardian figures, wearing a round-necked coat at royal tombs. The content of this study is as follows: First, the costumes worn by stone guardians are depicted, based on field investigation and 3D scan data. Second, the characteristics of costume are examined with reference to visual and literature historical records. Third, we compared and analysed the costumes of the Tang dynasty and ethnic groups of the West. Fourth, it is examined the implication of stone guardian’s costume, considering its relation between stone guardian wearing sleeveless armor(stone guardian1) and stone guardian wearing round-necked coat(stone guardian2). Stone guardian 2 is wearing a hairband, similar to Gun, which existed before Unification. Round-necked coat has narrow sleeve, side slit and foot length. This indicates that foot length co-existed with calf length in round-necked coat. The leather belt with metal ornaments is decorated with pochette and dagger. Boots have a round shoe cap, and their neck has a slope, high in the front and low at the back. It has been pointed out the similarity between the costume of Stone guardian 2 and Persia or Sogdian costume, based on the hairband and pochette. However, hairband was also worn in other regions of Central Asia and West Asia, making it difficult to define it solely as Sogdian tradition. Also, we have found the wearing of belt with hanging decoration of simple weaponry and pochette throughout Asia. Finally, Stone guardian figures of Unified Silla tombs are the result of embracing royal bodyguards’ costume of Tang dynasty. For costume of Stone guardians, it expresses the military-officials’ costume, and Stone guardian 1 is estimated to have higher social status than Stone guardian 2. Through Stone guardian 1, it shows the distinct feature of Silla especially through headgear. Moreover, the fact that Stone guardian 2 is wearing a hairband instead of bokdu is noted as the biggest difference between Silla and Tang. The combination of hairband and round-necked coat, furthermore, implicates diversity of the costume of Silla.