This study examines the relationship between cognitive flexibility and repetitive behaviors in children with autistic spectrum disorders (ASD). In the first study, a questionnaire survey was carried out to create a scale to directly assess the repetitive behaviors of children with ASD during the treatment and education. Subjects were 61 individuals who were therapists involved with the treatment and education. Factor analysis identified four sub-factors: “the difficulty of behavioral control”, “persistence in following rules”, “low level of resistance to uncomfortable situations”, and “circumscribed interest”. In the second study, a spontaneous card sorting test was performed by 15 children with ASD and 31 typically developing children to compare cognitive flexibility. The results showed no significant difference in cognitive flexibility between the children with ASD and typically developing children. On the other hand, when stimulation of the card is a concrete object, the children with ASD who had a high score on measures of “circumscribed interest” performed the classification from a variety of perspectives and showed a more flexible response.