The aims of this research was to get empirical evidence about the effect of
STAD method on Students’ Vocabulary Mastery and to identify the students’
achievement in learning vocabulary through STAD. this research used
quantitative method. The sample of this research were the first grade of Junior
High School 9 Purwokerto. With the total of students were 35 from each
group. The research conducted experiment in two different classes. First
group was using STAD (Students Team Achievement Division) method as
experimental class, and the second was using traditional method as control
class. The treatment was carried out for two weeks. The data were collected
through the achievement of pre-test and post-test from two groups. The result
showed that there was a significant difference between the experimental froup
and control group, t-test result 2.499 and t-table 1.671. STAD made students
more interested in material. So, it can be conclude that STAD method has
possitive effect to the first grade of Junior High School in teaching
vocabulary.