アブストラクト：
" High-z quasars were mainly observed at 1.6 and 5 GHz by VLBI. Therefore, we observed nine high-z quasars at 8.4 GHz by JVN in order to estimate their types. As a result, eight sources were detected by, at least, one baseline, and VLBI images were obtained for five of them. Additionally, five sources were showed flat or inverted spectrum. In conclusion, four sources of five were identified with FSRQ (candidate). Our result indicates that there are more blazar-like sources at high-z than previously thought. Next, we will observe 523 high-z quasars by the East-Asia VLBI Network to investigate the detailed radio structures. "