Among the researches on the workability of high fluidity concrete and the quality evaluation of the resulting structure, the basic experiment and the form lateral pressure experiment using a small mock test specimen were carried out and reported in this paper as the Part 1. The following findings were obtained. The high fluidity concrete was able to obtain the quality equivalent to the slump-controlled concrete even in a shortened compaction time of approx. 1/3. Also, it was found appropriate to examine the lateral pressure of the form as a hydraulic pressure.