This study examines public perception of ethicality of randomized field experiments of individuals living in Japan. Two online surveys are implemented targeting approximately, 2,000 respondents each. In the first survey, respondents are asked if they feel there are ethical issues with six past experiments conducted by economists. Among the six experiments, an experiment on the impact of preschools is considered as not unethical by the majority of the respondents. Conversely, a study on using the lottery to promote charitable giving is considered unethical by the majority. To further investigate the drivers behind the respondents stances on the ethics of the experiments, a second survey is conducted focusing on the above two experiments. Respondents are shown different, randomly assigned explanations of the experiment. To test whether the randomized control trial design itself is a cause of the respondents' stance, a study using a before-after comparison is also shown. The result shows that the difference in the experimental design alone does not affect the ethical issues for the study promoting charitable giving. Changing the topic of the study from charitable giving to the other pro-social behavior decreases the responses of "Unethical." Mitigating ethical issues in the experiments is required for evidence-based policymaking in Japan.