In this paper, we examine the effectiveness of Nudge messages, which are used to encourage early evacuation during heavy rain disasters. Based on a questionnaire survey of Hiroshima residents, we analyze the impact of behavioral economic messages on residents' intention to evacuate when a disaster occurs hypothetically. We also analyze the heterogeneity of message effectiveness. As a result of the analysis, it was clarified that messages which communicate social norms and potential externalities in terms of expressions of loss or gain are effective in activating the decision to evacuate. These messages have been shown to be effective for different types of residents, but appropriately less effective for those with no need to evacuate.