An apparatus for performing a processing operation on an object, comprising: a supporting frame; a conveying device, which defines a movement path; a supporting element which is coupled to the conveying device and which is moved by the conveying device along the movement path relative to the supporting frame, the supporting element defining a housing configured to house, in use, the object; and a processing unit which is associated with the movement path; the processing unit comprising: a supporting structure; a processing device, which is configured to perform, in use, the processing operation on the object placed in the housing, when the supporting element is at a processing station located along the movement path; at least one contact element, removably mounted on the supporting structure at least at the processing station, which defines a contact surface which provides a contact and supports the supporting element when the supporting element is in the processing station and the processing device performs, in use, said processing operation on the object; the processing unit also comprising an adjusting element and a fixing element, wherein: the adjusting element is mounted on the supporting structure and is adjustable relative to it along an adjusting line, to assume an operating position which is comprised between a first position and a second position; the at least one contact element is mounted on the supporting structure by means of a supporting portion which is removably coupled to the adjusting element, the operating position of the adjusting element determining an operating height of the contact surface relative to a floor on which the processing unit is positioned, the operating height being between a maximum height, relative to the floor, and a minimum height, relative to the floor; the contact surface is placed at the maximum height, when the adjusting element is in the first position, and at the minimum height, when the adjusting element is in the second position; and the fixing element is switchable between an operating configuration, in which it is coupled to the at least one contact element and constrains the at least one contact element to the supporting structure in order to keep the contact surface fixed at the operating height determined by the adjusting element, and a non-operating configuration, in which it is uncoupled from the at least one contact element and allows removal of the at least one contact element from the supporting structure and uncoupling of the at least one contact element from the adjusting element. a supporting frame; a conveying device, which defines a movement path; a supporting element which is coupled to the conveying device and which is moved by the conveying device along the movement path relative to the supporting frame, the supporting element defining a housing configured to house, in use, the object; and a processing unit which is associated with the movement path; a supporting structure; a processing device, which is configured to perform, in use, the processing operation on the object placed in the housing, when the supporting element is at a processing station located along the movement path; at least one contact element, removably mounted on the supporting structure at least at the processing station, which defines a contact surface which provides a contact and supports the supporting element when the supporting element is in the processing station and the processing device performs, in use, said processing operation on the object; the processing unit also comprising an adjusting element and a fixing element, wherein: the adjusting element is mounted on the supporting structure and is adjustable relative to it along an adjusting line, to assume an operating position which is comprised between a first position and a second position; the at least one contact element is mounted on the supporting structure by means of a supporting portion which is removably coupled to the adjusting element, the operating position of the adjusting element determining an operating height of the contact surface relative to a floor on which the processing unit is positioned, the operating height being between a maximum height, relative to the floor, and a minimum height, relative to the floor; the contact surface is placed at the maximum height, when the adjusting element is in the first position, and at the minimum height, when the adjusting element is in the second position; and the fixing element is switchable between an operating configuration, in which it is coupled to the at least one contact element and constrains the at least one contact element to the supporting structure in order to keep the contact surface fixed at the operating height determined by the adjusting element, and a non-operating configuration, in which it is uncoupled from the at least one contact element and allows removal of the at least one contact element from the supporting structure and uncoupling of the at least one contact element from the adjusting element.