A manufacturing method for manufacturing an image bearing unit from a material cartridge, the material cartridge including: an image bearing member; a frame including a first engaged portion; a supporting member including a fixed portion fixed to the frame, the supporting member including a bearing portion that supports the image bearing member, a through-hole, a second engaged portion opposed to the first engaged portion, and a cover portion; and a developing unit including a developing roller configured to develop a latent image formed on the image bearing member and an engaging portion (26a, 26b), the engaging portion (26a, 26b) engaging with the first engaged portion and the second engaged portion such that the developing unit is swingably coupled to the frame, the manufacturing method comprising a separating step for detaching the engaging portion (26a, 26b) from the first engaged portion and separating the developing unit from the frame, characterized in that the frame includes a projecting portion projecting toward an outer side of the frame in a rotation axis direction of the image bearing member, so as to penetrate the through-hole, the cover portion covers at least a part of the projecting portion penetrating the through-hole, the cover portion including a contact portion, the contact portion is configured to come into contact with the projecting portion when the supporting member is deformed to allow the second engaged portion to be detached from the engaging portion (26a, 26b) in a state in which the fixed portion is fixed to the frame, and in that the manufacturing method further comprises: a removing step for removing at least a part of the contact portion from the supporting member; and a deforming step for deforming the supporting member to allow the second engaged portion to be detached from the engaging portion (26a, 26b) in the state in which the fixed portion is fixed to the frame. the material cartridge including: an image bearing member; a frame including a first engaged portion; a supporting member including a fixed portion fixed to the frame, the supporting member including a bearing portion that supports the image bearing member, a through-hole, a second engaged portion opposed to the first engaged portion, and a cover portion; and a developing unit including a developing roller configured to develop a latent image formed on the image bearing member and an engaging portion (26a, 26b), the engaging portion (26a, 26b) engaging with the first engaged portion and the second engaged portion such that the developing unit is swingably coupled to the frame, an image bearing member; a frame including a first engaged portion; a supporting member including a fixed portion fixed to the frame, the supporting member including a bearing portion that supports the image bearing member, a through-hole, a second engaged portion opposed to the first engaged portion, and a cover portion; and a developing unit including a developing roller configured to develop a latent image formed on the image bearing member and an engaging portion (26a, 26b), the engaging portion (26a, 26b) engaging with the first engaged portion and the second engaged portion such that the developing unit is swingably coupled to the frame, the manufacturing method comprising a separating step for detaching the engaging portion (26a, 26b) from the first engaged portion and separating the developing unit from the frame, characterized in that the frame includes a projecting portion projecting toward an outer side of the frame in a rotation axis direction of the image bearing member, so as to penetrate the through-hole, the cover portion covers at least a part of the projecting portion penetrating the through-hole, the cover portion including a contact portion, the contact portion is configured to come into contact with the projecting portion when the supporting member is deformed to allow the second engaged portion to be detached from the engaging portion (26a, 26b) in a state in which the fixed portion is fixed to the frame, and in that the manufacturing method further comprises: a removing step for removing at least a part of the contact portion from the supporting member; and a deforming step for deforming the supporting member to allow the second engaged portion to be detached from the engaging portion (26a, 26b) in the state in which the fixed portion is fixed to the frame. a removing step for removing at least a part of the contact portion from the supporting member; and a deforming step for deforming the supporting member to allow the second engaged portion to be detached from the engaging portion (26a, 26b) in the state in which the fixed portion is fixed to the frame.