To facilitate the work execution of veranda in a building frame, and to enable the construction in a short period.

A boat-formed bottom frame 1, a fence wall 2, and a hand rail 3 are previously and separately formed, and furthermore, the fence wall 2 is divided to corner fence wall units 2A respectively having the nearly L- shaped plane and a front surface fence wall unit 2B in the condition that a surface side fence wall outer wall material is removed. In a construction field, each member is connected for fitting, and the handrail 3 is fitted over each member, and finally, the fence wall outer wall material is fitted to the fence wall 2 in response to the tone of the outer wall of a building frame.