This study investigated the influence of the short-term stay in US on junior college students' stereotype of American and self-evaluation of English ability. The followings were found through quantitative and qualitative analysis of the pre and post questionnaire and the instructor's observation; 1) the short-term stay in US tended to improve their stereotype of American and self-evaluation of English ability, 2) experience of staying with an American family and interaction with various Americans seem to have influenced their stereotype of American, 3) English classes they took in US might have changed their self-evaluation of listening ability, 4) students without prior homestay experience tended to have enjoyed more and had better impression of a host-family than those with such prior experience.