Alpine vegetation is considered to be sensitive to climate change. This assumption is supported by an increasing number of observational studies. Vegetation changes during the last decade at Mt. Komagatake in central Japan are reported. Four permanent quadrats of 1 m × 1 m at each of four plots (total 16 quadrats) are set and each quadrat is divided into 100 small grids (0.1 m × 0.1 m). All vascular plant species are recorded in each grid. Soil surface temperature (at depth of 1 cm) is automatically recorded with data loggers at 1-h intervals to determine the start day of the growing season and to calculate the effective cumulative soil temperature. Species numbers did not differ significantly between 2008 and 2017. However, total plant numbers did increase significantly in 2017 from those in 2008. At the study sites, effective cumulative soil temperatures partly explain the increase in total plant numbers. Dwarf shrubs had a tendency to increase compared to graminoids and forbs.