Among the abundance of research on learners' attitudes and motivation toward English learning, it has been pointed out that motivation tends to diminish with advancing age (Carrieira, 20061), Koiso, 20062)). This study examines the motivational structures of 444 students majoring in engineering in the 1st grade through the 3rd grade at a National College of Technology by administering a 50-item questionnaire to examine possible variation on a motivational scale over time. An exploratory factor analysis was performed with a promax rotation with the aim of extracting factors constituting the motivational construct. Furthermore, the correlation coefficients of the English proficiency scale and the overall attitudinal/motivational scale and each of the subscale indices were computed. The analysis extracted four factors: instrumental motivation, integrative motivation, negative learning experiences, and priority in the specialized area. The findings are: (1) the overall motivational scale was a little lower than the median value of 3.5, representing a rather low level of motivation, (2) no significant difference was found among the three grades in their overall motivational scales, (3) a significant difference was observed among the subscale indices only for the factor "priority in the specialized area", (4) the English proficiency of the 3rd grade was higher than those of the 1st and 2nd grade. Contrary to expectation, the students did not place a high priority in their specialized area, and it dropped as the students' grade in school advanced, indicating there was not so strong an influence of the specialized area subjects on learning English.