Emotional communication plays an important role in human social life. It involves how emotions are presented and recognized, but the rules of how emotions are expressed and decoded vary from culture to culture. The rule involves “masking” which means concealing a genuine emotion by displaying a different emotion that one does not genuinely feel. The current study examined cultural differences in the decoding of “masking” rule between Japanese and Chinese people when perceiving dynamic facial expressions. There were two research questions for the current study: 1) Do Japanese and Chinese participants would evaluate and decode masking smiles differently? 2) Are there cultural differences in attention to eye regions when perceiving dynamic facial expressions? The participants were displayed morphed-movie stimuli which changed angry to smiling face. Then, they were asked to evaluate the emotion of the actor. Their attention to eye regions while seeing the face changing movie was also measured using an eye tracker. Results indicated that, although there were no cultural differences in the subjective evaluations of emotions, the attention process while watching the changing facial expressions differed between cultures. Japanese people fixated longer in the eye regions compared to Chinese people when perceiving dynamic facial expressions. The current study provided empirical evidence of cultural differences in the applications of decoding rule of facial expressions within East Asian cultures.