The effective utilization of fly ash is positively studied in various fields and the utilization as raw material of concrete aggregate is one of the effective solutions. So far, the investigation of artificial lightweight aggregate made of fly ash has been carried out and some were put to practical use, but all of them are the foaming type aggregate. Now, different from such foaming type aggregate, "High Strength Artificial Aggregate" (hereinafter called FA aggregate) which has a dense structure through properly controlled production condition has been developed. In this report, the fundamental characteristics test of concrete which was carried out on concrete using FA aggregate made of fly ash as main raw material and with a water/cement ratio of 25 to 60% is discussed centering the comparison with those of concrete using natural aggregate (hereinafter called NA aggregate) and artificial lightweight aggregate in the market (hereinafter LA aggregate). The characteristics of fresh concrete and hardened concrete using FA aggregate have been studied based on the basic tests and following results are obtained. 1. The unit water content of the concrete using FA aggregate in case of ordinary strength region with AE agent tends to be smaller than those of the concrete using NA aggregate and LA aggregate. The workability of the concrete using FA aggregate is good as the same with those of the concrete using NA aggregate and LA aggregate. 2. As to the development of compressive strength of the concrete using FA aggregate, even in the high strength region exceeding 60N/mm^2. to say nothing of in the ordinary strength region, the same level of value with that of the concrete using NA aggregate is confirmed.