This study investigated the effects of different gloss locations in extensive reading readers on English reading abilities of elementary students. It examined four groups of sixth graders in an elementary school and an extensive reading class was conducted over sixteen weeks. The four groups were given graded readers with four different types of glosses, such as non-gloss, marginal gloss, footnote gloss, and endnote gloss. To verify the effects of this experiment, pre- and post-reading ability test for the cognitive domain and pre- and post-questionnaire for the affective domain were administered to see if there were any achievement in reading ability and affective domain. The findings were as follows: (1) The four groups showed improvement in the reading ability tests. This result indicates that extensive reading was effective in improving students' reading ability; (2) The footnote gloss group showed the greatest change. This result indicates that footnote glosses influenced the most in improving students' reading ability; (3) All the groups showed positive results in the affective domain including attitude, self-confidence, interest, expectation, and value. In conclusion, extensive reading made a positive effect on all four groups and footnote glosses proved to be the most effective in both cognitive and affective domain.