Dehydration of ethanol to ethene on acidic OH groups of zeolites was observed by infrared (IR) spectroscopy and temperature programmed desorption (TPD). The rate of decomposition of surface ethoxy groups was measured by measuring the amount of recovered acidic OH groups by IR, while confirming the evolution of ethene using a mass spectrometer, for the estimation of activation energy. The obtained activation energies for the evolution of ethene from ethoxy groups on hydrogen form mordenite, ZSM-5, and ferrierite zeolites were 161 ± 6, 181 ± 2, and 188 ± 2 kJ·mol−1, respectively. A tendency was found that the activation energy became larger in smaller-pored zeolite. The cause of the difference of three zeolites in activation energy for ethene evolution from ethoxy species is discussed along with an energy diagram described from reported theoretical examinations.