Drilling device for horizontal drilling having - a drill head, - a drill rod, at the borehole-sided end of which a drill head is arranged, and - a drive means which is arranged at the other end of the drill rod and is designed for the rotational driving and feed driving of the drill rod, - wherein the drill rod has an outer rod and an inner rod rotatably supported relative thereto, which are each composed of at least two drill rod elements, between which an annular space is designed for passing a flushing liquid from a rotary connection to the drill head, - the inner rod comprises an alignment space, which extends from the drive means up to a terminal element on the drill head side, and - in the alignment space at least a part of a target means for directional monitoring of the drill head is arranged, characterized in that - the inner rod is driven in a rotating manner by a first rotary drive and the outer rod is driven in a rotating manner by a second rotary drive independent of the first rotary drive, - in that a control means is provided, through which the first rotary drive and the second rotary drive can be set and controlled independently of each other, - in that at its end on the drill head side each drill rod element has an adjusting means, by which a defined installation position of a drill rod element of the inner rod to a surrounding drill rod element of the outer rod is predetermined, and - in that at the end of the drill rod elements at least of the inner rod or the outer rod facing away from the drill head a marking element is arranged, through which the position of the drill rod element relative to the drill head is visible. - a drill head, - a drill rod, at the borehole-sided end of which a drill head is arranged, and - a drive means which is arranged at the other end of the drill rod and is designed for the rotational driving and feed driving of the drill rod, - wherein the drill rod has an outer rod and an inner rod rotatably supported relative thereto, which are each composed of at least two drill rod elements, between which an annular space is designed for passing a flushing liquid from a rotary connection to the drill head, - the inner rod comprises an alignment space, which extends from the drive means up to a terminal element on the drill head side, and - in the alignment space at least a part of a target means for directional monitoring of the drill head is arranged, - the inner rod is driven in a rotating manner by a first rotary drive and the outer rod is driven in a rotating manner by a second rotary drive independent of the first rotary drive, - in that a control means is provided, through which the first rotary drive and the second rotary drive can be set and controlled independently of each other, - in that at its end on the drill head side each drill rod element has an adjusting means, by which a defined installation position of a drill rod element of the inner rod to a surrounding drill rod element of the outer rod is predetermined, and - in that at the end of the drill rod elements at least of the inner rod or the outer rod facing away from the drill head a marking element is arranged, through which the position of the drill rod element relative to the drill head is visible.