Fluorescent, ubiquitination-based cell cycle indicator-expressing HeLa cells have been irradiated with a microbeam set-up at RIKEN for examining the effect to cell cycle after bombarding with protons of 1 MeV incident energy. Here, single cells were exposed in their nucleus with different doses (100, 1000, 10,000 and 100,000 protons). Subsequently, the cells were monitored using time-lapse microscopy after irradiation. In this paper, we present the preliminary results for such irradiation for 8 cells. The irradiated cells with up to 10,000 protons showed the change in fluorescence from red to green. This indicates that the transformation from G1 to S/G2 in cell cycle seemed not to be affected by the irradiation up to 10,000 protons. However, the irradiated cell with 100,000 protons died in red fluorescence at 4 h after the irradiation.