Internal Combustion Engine is required High Efficiency/High Power, so that Combustion Pressure is increased more than before.By the way, Cylinder Head, which is main part of Internal Combustion Engine, should be required high reliability in user's needs. If there were once appeared trouble, reasonable troubleshootings could hardly be founded, so initial development schedule could not been attained occasionally. Because following reasons should be considered: Shape of Cylinder Head is very complicated. It's thermal phenomenon, which is composed of heat generation (by combustion), heat transfer (by combustion, cooling-water, intake air, exhaust gas) and heat conduction (by Cylinder Block, Valve Seat and Injection Nozzle). Now, in this report, heat transfer/thernal analysis for Cylinder Heads is introduced because it's accuracy has come to practical level.