PROBLEM TO BE SOLVED : To provide a building with a space appropriate for a specific use in such a manner that a core section of the building serves as a definite module; and to provide a real estate securitizing system which adapts a building to an arbitrary use by changing an exterior facing section so as to change a shape of an outer shape of the building, which achieves a reduction in the cost of design and building, the shortening of a building period, etc., and which can solve the problems on risks such as a risk of a decline of a land price, a risk of a long-term decrease in rent, a risk of a long-term rise in interest rate, while targeting at the building.SOLUTION : This building structure is composed of the core structure which for determining the substantial of the building, and the exterior facing structure for determining a shape of an outer peripheral section; both the structure are connected by means of a separable connecting member; a first floor section of the core structure serves as a business space; and upper floors as high as/higher than the second floor serve as a self-propelled parking space.