PROBLEM TO BE SOLVED: To constitute a sealed fitting part with few components and at a low cost using a simple injection molding method. SOLUTION: In this fitting structure of a developer container with a cabinet in which a developer storage chamber is formed and having an opening on one end and a cap which is fitted in the opening to block the opening, the cap consists of material having tensile modulus of elasticity smaller than that of the cabinet. The cap has a groove part which accepts all over perimeter of an outer edge part of the opening and the developer storage chamber is sealed by press fit by the outer edge part in the groove part. The cap has a side wall which blocks the opening, an inner peripheral wall projecting from the side wall and a peripheral wall projecting from the side wall so as to surround the inner peripheral wall from the outside. Inside dimension of the outer edge part is larger than outside dimension of the inner peripheral wall. Outside dimension of the outer edge part is smaller than inside dimension of the peripheral wall. The inner peripheral wall has a chamfering part formed over all the perimeter of the periphery at a corner part on the periphery side, dimension of the chamfering part is larger than difference between inside dimension of the outer edge part and outside dimension of the inner peripheral wall. COPYRIGHT: (C)2005,JPO&NCIPI
