Purpose of the study: The objective of this research was to explain the results of the development of instruments to assess the students' affective based on scientific approaches in the EFL class.Methodology: This study used the ADDIE method that consists of five steps: (1) analyzing, (2) designing, (3) developing, (4) implementing, and (5) evaluating. There were some instruments of the research used to gather the data such as the expert's validation sheet and questionnaire. Statistical

more »

... used in this research were Alpha Cronbach, the test of normality Kolmogorov-Smirnov, the test of homogeneity Levene, the test of linearity, the test of correlational Pearson, test of regression, and Wilcoxon test.Main Findings: The result showed that the development of an instrument to evaluate students' affective based on scientific approach was considered by some items, e.g. phases in scientific approach, skills in English language teaching, learning experiences, affective aspects, and indicator of assessment. Finally, it can be stated that (1) the instrument was valid with the mean Score in rank between 1-124 is 114.8; (2) the instrument reliable with the Score is 0.754; (3) the instrument was tested with the Asymp. Sig score of 0.042.Applications of this study: This study proved that the instrument of affective assessment was valid, practice, and effective to be used by the English teachers in assessing the students' affective during the teaching and learning process at the EFL classroom.Novelty/Originality of this study: The success of a student is not only measured based on the cognitive aspect but also based on the affective aspect.