To provide a filter mounting structure that allows a filter to be installed to a filter casing through a simple operation.

The filter mounting structure is composed of a slide body, a fixing member for regulating the slide body so as to be slidable, a filter pressing member, a first connection member for connecting them, a turning member turning around the fulcrum provided outside the slide body, and a second connection member for connecting the end part of the slide body to the turning member. The slide body includes a first long hole long in an oblique direction. The filter pressing member has a second long hole long in a pressing direction while the first connection member is inserted in the first long hole and the second long hole to be fixed to the fixing member, so that the filter pressing member is moved in the direction on the air inflow or outflow side of the filter casing by turning the turning member to press the filter to the filter casing.