Background and Purpose: The study aims to clarify the effects of physical environment on children's feeling and behavior for improving healthcare environment. Under the circumstances of poorly designed Japanese children's hospital, we investigated a couple of innovative American children's hospital recently built. The study focused on children's play environment especially on hospital playroom in this time. Within this decade, new unique children's hospitals have been built in the US, which focus more on children's sensitivity, behavior, and scale. These hospitals look different from other hospitals. This might be partly result from several researches in psychology and sociology field, to claim that children's healthcare environment should have own feature and be different from adult's one.