PURPOSE: To provide a new rack plate installation structure in which removal or drop of a rack plate can be prevented in a type in which dowels are used in containing bodies for installing the rack plate at a desired height position detachably by holding its engagement with the dowels even when force acting in such a direction to lift up the rack plate from under is applied after installation.

CONSTITUTION: In a containing body composed of side plates, a bottom plate, and a top plate, dowels are installed on inner surfaces of the side plates, and dowel holes for the dowels to be inserted for engagement are provided at one side end part of the rack plate, and a rack receiving groove for the dowels to be placed for engagement is provided at the other side end back surface part. The dowels protruded from one side plate are inserted into the dowel holes formed at one side end part of the rack plate for engagement, and the dowels protruded from the other side plate are placed on the rack receiving groove formed at the other end back surface for engagement for installing the rack plate.