The purpose of this study is to examine the effects of filial therapy that the parent solve problems from the play in the home, on the relaxation of separation anxiety and the improving relation between. parent and child. The subject used in this study was an 4-years old boy and the filial therapy had given to him for 9 months. In the first place, the parent was trained play therapy technique from the researcher. In the next place, the parent as an play therapist had the play therapy in the home. The play situations recorded on video tape and audio tape. Tapes were transcribed. And the degree of improving the subject 's behavior analyzed from transcribed data. And the researcher compared the improving relation between parent and chikl using MIM(Marschak Interaction Method). The result of the present study is summarized as following: (1) The filial therapy had effect on improving relations between parent and child. (2) The filial therapy had effect on the relaxation of subject's separation anxiety about parent.