Fixing device and image forming apparatus with a cover for generating a stable nipping pressure on a conveyance roller pair

A fixing device includes a housing, a cover member pivotally mounted on the housing, and operable to change the posture thereof between a closing posture and an opening posture, and a first and second urging member. A first conveyance roller for conveying a sheet is rotatably supported on the housing, and a second conveyance roller to be pressingly contacted with the first conveyance roller is rotatably supported on the cover member. The first urging member applies, to the cover member in the opening posture, an urging force for returning the cover member from the opening posture to an intermediate posture between the opening posture and the closing posture. The second urging member applies, to the second conveyance roller, an urging force with which the second conveyance roller is pressingly contacted with the first conveyance roller when the cover member is in the closing posture.