A partition wall has a structure with a wall end portion butted against another building structure and exposed to architectural spaces. An end post at the end portion of the wall is constituted from first and second end post elements, which are spaced apart from each other, so that a gap or an isolation zone interrupting a propagation of a solid vibration or insulating a path for propagating the solid vibration is formed between the first and second elements. An interior finishing panel for defining the architectural space on one side of the wall is fixed to the first element and the interior finishing panel for defining the architectural space on an opposite side of the wall is fixed to the second element.