The ongoing global warming likely affects performance of marine animals although its impacts may vary among populations experiencing different thermal regime and among species which live under different conditions. In general, species which can persist in warming sea water are considered to have high thermal tolerance. We examined within and among-species variation in thermal tolerance of sea anemones by indoor tank experiment. In this experiment, we compared the survivorship between different species, Diadumene lineata (intertidal species) and Metridium senile (subtidal species) from the same region (Hokkaido), and between different populations of D.lineata from the two regions (Hokkaido and Chiba). We found that the upper thermal limit of the two species from Hokkaido was higher for the intertidal D.lineata, and that of two populations of D.lineata from the different regions was the same. Variation in habitat condition (subtidal, intertidal) may be related to the observed among-species variation in thermal tolerance, whereas the variation in the original habitat temperature does not affect the thermal tolerance of D.lineata.