Heat treatment of tobacco represented by heating and steaming is of crucial importance in the tobacco industry because it influences the quality of cigarettes such as their aroma and taste. The rates of these changes depend on the temperature and the moisture content of the tobacco. The objective of this study was to identify the change rate of some constituents related to aroma and taste during heat treatment. A sample vessel packed with a filler of flue-cured tobacco was put into a through-flow heating unit. The air at 60% or 80% relative humidity had been adjusted beforehand to a prescribed temperature in a range of 333 K to 353 K, and the flow rate of the air had been adjusted to 3 m/s. After the prescribed time, all of the filler was taken out of the unit. The constituents of the filler were extracted with several organic solvents and the yields were determined by gas chromatography. The concentration of the constituents decreased with increasing temperature, and the concentration of nicotine decreased with increasing humidity of the air. The changes in concentrations could be approximated to pseudo first-order reactions. Moreover, the temperature dependence of the rate constant could be expressed by the Arrhenius equation, which allows to obtain the activation energy and frequency factor as parameters of the equation. The curves of the concentrations calculated with the parameters were in agreement with each experimental value under various heating conditions. Therefore, it was concluded that the simplification and the parameters of the reaction are valid.