This research aims to develop instrument for assessing student's affective domain using self-assessment (SA) and peer-assessment (PA) models employs the modified model of development by Mccoach. The sampling technique used was cluster random sampling. Aiken, CFA second order and alpha cronbanch were used as the data analysis techniques, aided by Excel program, Lisrel and SPSS. The results show that the there were 6 constructs of instrument for assessing student's affective domain. The content validity was done using Aiken index and the result ranged from 0,750-1,00 and all of the items were valid. The construct validity of the instrument was done using CFA approach. A fit model of instrument for affective domain based on self-assessment was developed with the value of Chi-square (X^2) = 267,22 df = 246, P-value = 0,168, RMSEA = 0,022 and the instrument-based on peer-assessment has the value of Chi-Square (X^2) = 151,55, df = 126, P-value = 0,060, RMSEA = 0,034. On the items estimation, the value of loading factor was 0,31-0,99 (>0,30) which means that the items in the instruments based on SA and PA are valid. The instruments reliability reached 0,788-0,886 which means that all the instruments developed were valid. The valid instrument is very important to get good information about self-assessment and peer-assessment.