School trips abroad undertaken by high schools in Japan provide opportunities for students to raise motivation to learn English through intercultural experiences. To probe precise changes in students’ motivation before and after the trips, the author asked 487 students in two schools to answer a questionnaire based upon Self-Determination Theory. A conspicuous difference of the trip programs in the schools is the destination country: School A to Taiwan and School B to Malaysia. The students from School B had opportunities to communicate with Malaysian students in English whereas those from School A had fewer opportunities to use English. After the trip in the School B, the number of the students who are not motivated to learn English more than before decreased,and the number of more motivated students increased. On the other hand, the students from School A did not show significant changes in motivation. Answers from the questionnaires show, however, that a large number of students find English indispensable for their future career. These results suggest that intercultural experiences, especially some interactions in English with student swith different cultural background, would provide effective incentives to learn English.