Performance assessment has been introduced to school education as an alternative measure of the former educational assessment which put much emphasis on the result rather than the process of learning, memorization than pursuit of knowledge, and passive than active study. As for the subject of mathematics, the change of the assessment came to replace multiple choice tests with descriptive- and statement-type tests. This means animprovement on the testing system, focusing on the process of finding out the answer. The main focus, however, is still on the intellectual domain without paying due attention to the emotional domain of mathematics education. The previous studies on the assessment of emotional domain In mathematics have shown that there are stumbling blocks in the application of the assessment, such as the disputes on the reliability, objectivity, and fairness as well as the complicated procedure of applying the results to school records. The lack of the development and supply of the appropriate assessment tools have also been pointed out. Therefore, this study has been carried out with the intention of establishing an applicable standard of assessment on the emotional domain of high school matematics. As a result, detailed standards of performance assessment, which adopt oral examination, discussion, observation, and report have been developed. The problems which are likely to emerge In the course of the application of the newly developed assessment are under study as a continuing research project.