The relationship between autism and schizophrenia has been denied from the symptomatological and epidemiological standpoints. However, the mechanism whereby psychotic symptoms appear in association with autism has not been investigated at any length. Therefore, an investigation was conducted on how the unique modes of perception in autism are related to the psychotic symptoms observed. Through the therapy of one case of adolescent autism, the author points out the existence of physiognomic perception and vitality affect as characteristic modes of perception in autism. It was inferred that should autistics be placed under circumstances forcing them to withdraw from open communalism, their unique interpretation of the environmental world could give rise to psychopathological phenomena which would be considered delusional perception.