In this study, concrete with a slump flow of about 45 cm was used to study mechanically-compacting flowable concrete to establish specific compaction methods according to the geometry of the structure and the reinforcement distribution conditions. The results of the compaction tests showed that the vibratory force of a bar vibrator had a more significant effect on the propagation of vibrations during compaction than when the mix was varied within the range where mechanically-compacting flowable concrete is practically feasible, indicating that the type and capacity of the bar vibrator should be taken into consideration when setting the compaction method. Through verification of the validity of the setting of the compaction method by actual construction experiments, a method was proposed to set the compaction method based on the relationship between the rod vibrator used, the construction conditions, the compaction time that allows filling, and the compaction interval, and to determine the degree of compaction by the flow gradient.