This longitudinal study examined the development of spatial knowledge in a house from the model of a child's own house, using the model house kit. The second experiment was conducted after 2 years in the same way as the first one. The experiment involved 12 primary school children (3-6 grade) who had participated in the former experiment. Compared with the both results, we analyzed their advances from following aspects. 1) Making-procedure analysis showed that the thought process had the tendency to remain unchanged for two years. At a certain stage in development, children got the new observing point and they extended the understanding. 2) Comparing the room-position of the model and the house plan revealed that to understand the room location was rather easy, but to grasp the scale was difficult for children.3) The third stage of spatial cognition, comprehension of the exact location of rooms, was attained at roughly 3 grade.