The invention is aimed at increasing working efficiency of fixed hours such that a front cabin wall is embedded with the front part of a car framework. The frame-shaped front cabin wall is embedded from the front part to the fixed position between first supports (32) left and right of the front part of the left and right car frameworks. First bolts (33) inserted outside from the car width direction enable two side parts of the left and right of the front cabin wall (15) to be fixed on the first supports (32) on the left and right. At this time, due to the fact that the first supports (32) on the left and right can be opened from the front ends to the car width direction, the front cabin wall (15) can be guided into a guiding part (32d) at the fixed position. Therefore, only by embedding the front cabin wall (15) between the first supports (31) on the left and right from the front part, that is, the front cabin wall (15) can be automatically guided to the fixed position by the guiding part (32d) such that the front cabin wall (15) is fixed by the first bolts (33).