In recent years, there has been an increase in the number of invasive bamboos in forests and the concern about their impact on nursery management when reforestation is carried out. In this study, after clear-cutting of a Japanese cedar forest infested with moso bamboo, the regenerating culms were continuously mowed once a month for four years to investigate how the regenerating culms decayed. In addition, the occurrence of regrowth culms after five years was compared with the case of ordinary clearing underbrush. Many thick culms had regenerated at the time of new bamboo emergence but became thinner with each passing month. This resulted in the decrease in the number of culms generated. This cycle was repeated for several years, and it was seen that the number of generated culms became much lower in the fourth year. Additionally, the type of culms generated showed a shift in the order of large culms, resulting in small culms and grass-like culms. It was found that the eradicating effect of normal undercutting in reforestation was lower than that of continuous harvesting and was time consuming. In addition, the results suggested that the establishment of a working road at the time of reforestation was highly effective in suppressing the regeneration of bamboo by dividing the rhizome. Therefore, it is considered as desirable to establish a work road that divides the mother bamboo forest and the reforested area.