A roller cover, which is to be attached to a housing, the roller cover comprising: a protecting portion, which faces the circumference of the roller when the roller cover is attached to the housing; a first end portion, which is provided at one side of the protecting portion in an orthogonal direction; a second end portion; a first opposite portion, which is formed continuously with the first end portion, wherein the first opposite portion is fitted to one side of the housing in the orthogonal direction; and a second opposite portion fitted to the other side of the housing, wherein a first distance between the first opposite portion and the second opposite portion increases during an attachment operation, and wherein, when the attachment operation is completed, a final distance between the first opposite portion and the second opposite portion is less than maximum value of the first distance.