The purpose of the present study was to investigate the relationship between the perception of causality and the visual ability to segregate a moving stimulus into two phases of movement in young children. In Exp. I accuracy in judging the temporal order and the velocity difference of two movements in a causal stimulus were used as parameters for the ability of segregation. The results showed that young children who made a correct judgement on the two parameters had a tendency to report the launching response as the causal stimulus. In Exp. II the accuracy in the perception of a moving object, briefly halted halfway through, was used as a parameter in order to confirm the result of Exp. I. It was found that subjects who were classified into the higher ability group in the segregation of movement showed launching responses to causal stimuli more frequently than those who were classified as the lower ability group. In summary, it was concluded that the ability to segregate a movement is an important factor for young children to perceive a causal relation in a stimulus.