An image forming apparatus comprising a toner accumulating member disposed nearer to the housing than the cleaning blade and the lower seal are, wherein the toner accumulating member accumulates the toner at a tip of the cleaning blade; the toner accumulating member has at least one opening; and the following condition is satisfied:
0%<S(O)/S(C)<50%
wherein S(O) is a total opening area obtained by summing areas of all openings; and S(C) is an area of a rectangle defined by two sides having the same length as a length of the cleaning blade in its longitudinal direction and two sides having the same length as a distance between the lower end of the toner accumulating member and a position at the same height on the toner accumulating member as the lower end of the cleaning blade.