An image forming apparatus includes an image forming unit, a fixing unit, a heating portion, a duct with a suction opening and an exhaust opening, a fan connected to the exhaust opening and a sheet-like filter provided with a base layer and a collecting layer laminated on the base layer. The filter is disposed so that the collecting layer is inside and the base layer is outside and the filter becomes a convex shape to the outside from the suction opening. When a width of the suction opening is d1, and a maximum height of the filter from an imaginary surface passing through an edge portion of the suction opening is L, the filter satisfies 0.003