Abstract: The known method for constructing a tunnel of the type in which a shield tunnelling machine is shoved by means of a concrete lining jack and a shield jack equipped on the shield tunnelling machine with reaction forces received by concrete for lining placed in a space delimited by an inner form assembled within a tunnel bore successively dug by the shield tunnelling machine, a shield tail and an already placed concrete lining, as well as by the inner form, is improved in order to construct a main tunnel body as a reinforced concrete structure. The improvements include in that a reinforcing steel cage is mounted to a combined spreader and end form of the concrete lining jack via metal mounts, the placed concrete for lining is compressed while the reinforcing steel cage is moved, and thereby the reinforcing steel cage is disposed at a predetermined position within the concrete for lining by adjusting the stroke of the concrete lining jack.