The purpose of this study is to investigate the effects of participation in a play evaluation after free-choice activity on the language development of five-year-olds. The experiment group included 20 five-year-olds at A Daycare Center in J City, and the comparison group included 20 five-year-olds at B Daycare Center. Employed in the study to measure young children's language ability were the Receptive and Expressive Vocabulary Test and the Sentence Comprehension Test. As for statistical techniques for data analysis, the SPSS 19.0 program was used to conduct the independent sample t-test after the pre-test to examine homogeneity between the experiment and comparison group. The independent sample t-test was also performed for differences between the pre- and post-test results of the experiment and comparison group to examine the effects of play evaluation after free-choice activity on the development of young children's language ability. The findings were as follows: play evaluation after free-choice activity turned out to have effects on the development of young children's language ability including expressive and receptive language and sentence comprehension. These findings indicate that young children got to use various vocabulary words to which they were exposed while hearing the verbal expressions of their peers and develop the ability of gathering opinions from many people and building them into a common meaning in play evaluation after free-choice activity, thus improving their language ability.