The purpose of this study is to examine the educational effects of STEAM class by focusing on 21st century learner competencies based on burning and extinguishing unit. Two 6th grade classes were divided into experimental group and comparison group to treat the experimental group with elementary science class using STEAM class. General class according to teacher manual was implemented for the comparison group. Elementary science class applying STEAM class was conducted for 9 lessons throughout the experimental period. The result of this study are as follows. Elementary science class with STEAM class had significant effect on 21st century learner competencies compared to traditional instructor-led classroom. Looking specifically, it was a significant difference in the three domains of the seven domains (problem solving, collaboration, flexibility). The study results indicated that STEAM class was effective in improving learners`recognition of 21st century learner competencies.