To provide a louver blade fitting structure that can support a louver blade stably even though it is enlarged in size.

A support pole 100 is installed upright with an appropriate interval. A longitudinal directional edge of a louver blade 40, or more preferably its central part in the width direction is fixed to each support pole 100 and between the support poles 100 and 100 the louver blade 40 is installed. Compared with a conventional case in which only the edge of each louver blade in the width direction is fixed and supported in a cantilever fashion, it is possible to increase the installation strength significantly and both the size and the weight of the louver blade, especially its length in the width direction can be safely made larger.