The study is to find out relationship between social adaptive skills and rearing attitude of parents of children with mental retardation, and then is investigate factors of rearing attitude of parents of children with mental retardation influencing to their social competencies. The conclusions of this study are as follows; First, rearing attitude of parents of children with mental retardation is high in order of affective attitude, and autonomous, refusal, control attitude. Rearing attitude according to variables is more affective and autonomous in order of age, schooling, income, religion, first child, child attending elementary school, and schoolboy.Second, social competencies in children with mental retardation appear to level of subaverage. Social competencies according to sub-domains is high in order of play activities in children with mental retardation, social, rule and law, interpersonal skills, self-esteem, self care, and responsibility. Social competencies according to school year is high in order of middle school 3 grade group, middle school 1 grade, middle school 2 grade, elementary school 1, 2 grade group, and 3, 4 grade. In gender, schoolboy is high than schoolgirl, as well is high social, play activities, rule and law, interpersonal skills, responsibility and self care, while schoolgirl is high than schoolboy in self-esteem. Third, there are significant correlation between rearing attitude of parents of children with mental retardation and social competencies. Especially, there are significant correlation at sub-domains of social competencies in autonomous rearing attitude. Therefore, the findings showed that the more rearing attitude of parents of children with mental retardation is autonomous, the more social competencies in children with mental retardation is improve.