The growth and size variation of rotifer (Brachionus plicatils) were examined at the various water temepratures ranging form 18 to $36^{circ}C$, and under continuous light condition. Either Chlorella ellipsoidea or $omega$-yeast were fed to rotifer as a food organism. Compared to large-type rotifer fed of $omega$-yeast, those fed on C. ellipsoildea generally showed higher growth at 7th after starting culture under the water temperaure of less than $30^{circ}C$. Above such temperature, the large-type rotifer fed on $omega$-yeast showed higher growth rather than those fed on C. ellipsoidea and the maximum cell number reached 1,420 ind./m$ell$ at $36^{circ}C$, whereas when the small-type rotifer was fed on $omega$-teast, its maximum cell number was to be 1,669 ind./m$ell$at $34^{circ}C$. The striking decrease in size was found in large-type rotifer which was to be $112.1mu m$m(initial : 202.0${mu}{ extrm}{m}$) when they were fed on C. ellipsoidea at $34^{circ}C$ for 5 days after starting culture. A great increase in size from the initial of 157.0 to $201.3mu m$mwas show in small-type rotifer fed on $omega$-yeast at $20^{circ}C$,for 5 days. The present results demonstrated that size variation of rotifer could be controlled by changing culture temperature.