This study investigates expressions of propositional modality (epistemic and evidential) in Japanese and Chinese. It aims to highlight some fundamental characteristics of and differences between the modal systems in the two languages. It has been found that adverbs in Chinese play a more important role than adverbs in Japanese in expressing modal meanings. This study has also found that more modal expressions are used in the Japanese text than in the Chinese translations. That is to say, Chinese language speakers seem to prefer straightforward assertions to marked epistemic forms. In other words, Chinese speakers often choose realis modality when describing things, situations or their own ideas, unless the speaker thinks it is very necessary to clearly indicate that the proposition is not an absolute fact, or has not been confirmed to be a truth. Data of this study are collected from a Japanese-Chinese bilingual corpus, and the discussion is based on a concept of realis/irrealis.