The purpose of this experimental research is to determine how song-focused musical activity has effects on the self-expression and positive thoughts on intellectually disabled workers. The subjects of the study were intellectually disabled workers who were working at occupational rehabilitation agencies in C and G area. A song-focused musical activity was conducted for workers who agreed to participate. Pre and post scores were measured by utilizing a self-expression scale and positive thought scale before and after the song-focused musical activity. The result were as follows. First, there was a meaningful distinction between the experimental group that participated in song-focused musical activity and the control group that did not. There was no meaningful distinction in the verbal expression scope. However, there was a meaningful distinction between the phonetic and nonverbal scopes. Second, there was a meaningful positive thought score between the experimental and controlled groups. Moreover, significant changes were found in the sub factor of subjective satisfaction. However, there were no significant changes in the sub factor of pursuit of goal. It was found out that song-focused musical activity has positive effects on the intellectually disabled workers in self-expression and positive thoughts.