To provide a building in which a person can easily and surely come and go between floors with different heights, by securing a traffic line for making the floors with the different heights communicate with each other.

In this building A equipped with upper and lower stories 2 and 1, a first intermediate floor 1b is provided on a part of the floor 1a of the lower story, and a second intermediate floor 2b is provided on a part of the floor 2a of the upper story. In the approximate center of a building body A1, a staircase 30 is installed along the vertical direction of the building body A1, and provided with first-third stairways 31, 32 and 33 for making the floors 1a, 1b, 2a and 2b communicate with one another. At least either a room or a storage room is installed on each of the floors 1a, 1b, 2a and 2b in such a manner as to be adjacent to the staircase 30. Thus, the staircase as the traffic line for making the floors with the different heights communicate with each other can be secured in the approximate center of the building body, and the person can easily and securely come and go between the floors with the different heights.