The lack of natural fine aggregate in Japan is serious because the commitment to protect the natural environment is increasing. Many concrete engineers are eager to find fine aggregate sources other than the traditional river and sea sand. Copper slag fine aggregate is expected to be one of the alternatives although the location where the copper slag is available is limited. In this paper, some characteristics of concrete with copper slag will be clarified. The carbonated thickness, resistance to freezing and thawing, thermal resistance, shrinkage strain, creep and setting time have been examined. The strength, slump and durability of concrete with copper slag are not inferior to those of normal concrete. However, copper slag sometimes delays the setting time of concrete even if it is produced at the same refinery. The delay of setting time is more than one week in some cases, although the durability in concrete is not affected by it. The main reason will be determined and the solution will be given in this paper.