A fixing device includes a heating member disposed with an internal heating source and a pressuring member that presses against the heating member. The fixing device is configured to be attachable to and detachable from an image forming apparatus body, and includes: brackets that retain the heating member; pressuring levers that retain the pressuring member and are movably supported in the brackets; urging means that push the pressuring levers in a direction where the pressuring member presses against the heating member; and cams that are rotatably supported in the brackets, contact the pressuring levers, and adjust the pressuring force of the pressuring member.