The objective of this thesis is to suggest a design guideline for a teaching assistant robot by clarifying what images satisfy the role of a teaching assistant robot, and by finding out what elements of body feature epitomize such images. Images of teaching assistant robots were established from a literature review and factor analysis. And eight elements of body feature were extracted from human form. Robotic external form samples varied according to the elements of body feature, which was modeled three-dimensionally. Children, who are the main users of teaching assistant robots, evaluated the 3D robot samples projected onto a wall in real size. The evaluation criteria were the role images of teaching assistant robots, demographic features about age and gender, preference, and appropriateness. The results of evaluation were analyzed by analysis of variance, and analysis of correlation. Finally, a design guideline for a teaching assistant robot was suggested based on the results of the experiment about the correlation between elements of body feature and role images.