Heat input generated in plate by gas cutting process was determined quantitatively. And, the feature of distribution of heat input along the thickness was clarified. First of all, the heat input distribution of the preheating flame was examined. Next, about the gas cutting process, the method of predicting the heat input was proposed, and the predicted values were compared with the experimental values. Finally, the inherent strain distribution along the thickness was measured, and the heat input distribution along the thickness was examined. The main conclusions obtained were as the following: 1) It was able to explain the heat input distribution of the preheating flame as gaussian distribution. 2) It was shown that the proposed method of presuming the heat input in plate generated by gas cutting was appropriate. 3) The distribution of heat input by gas cutting along thickness is effected by preheating gas flame and dross.