WC connection device for connecting a shower WC to a wall, having a mounting frame which is composed of at least two vertical metal profile struts (2.1, 2.2) and at least one crossbeam (2.5) connecting the metal profile struts, the front side of the mounting frame defining a planking plane, with a flushing box having a front box wall (9.1) defining a first, substantially vertical plane, with a flushing water pipe connected to the flushing box, with a drain pipe bend arranged below the flushing water pipe in the assembled state of the WC connection device, and with a guide channel connected to the flushing box for receiving a flexible water supply line for a bidet-shower arranged in the shower WC, wherein a lower end (10.1) of the guide channel opens in a height region delimited by an upper end (8.41) of an outlet opening (8.4) of the flushing water pipe and a lower end (4.11) of an inlet opening (4.1) of the drain pipe bend, and wherein the lower end (10.1) of the guide channel is arranged relative to a second vertical plane which is transverse to the first, substantially vertical plane and in which the central axis of the outlet opening (8.4) of the flushing water pipe lies, such that the lower end (10.1) of the guide channel lies in overlap with the second vertical plane or is spaced from the second vertical plane by a dimension which is smaller than the inner diameter of the inlet opening (4.1) of the drain pipe bend, characterized in that the lower end (10.1) of the guide channel is oriented in such a way that the central axis of the guide channel at the mouth of the lower end (10.1) is not more than 45° offset, preferably not more than 30° offset, particularly preferably not more than 15° offset relative to the first vertical plane defined by the front box wall (9. 1) or runs parallel to this first plane, and in that the WC connection device is provided with an installation set which comprises the water supply line to be introduced into the guide channel, the water supply line being longer than the guide channel by at least 15%, preferably at least 25%, particularly preferably at least 30%. with a flushing box having a front box wall (9.1) defining a first, substantially vertical plane, with a flushing water pipe connected to the flushing box, with a drain pipe bend arranged below the flushing water pipe in the assembled state of the WC connection device, and with a guide channel connected to the flushing box for receiving a flexible water supply line for a bidet-shower arranged in the shower WC, wherein a lower end (10.1) of the guide channel opens in a height region delimited by an upper end (8.41) of an outlet opening (8.4) of the flushing water pipe and a lower end (4.11) of an inlet opening (4.1) of the drain pipe bend, and wherein the lower end (10.1) of the guide channel is arranged relative to a second vertical plane which is transverse to the first, substantially vertical plane and in which the central axis of the outlet opening (8.4) of the flushing water pipe lies, such that the lower end (10.1) of the guide channel lies in overlap with the second vertical plane or is spaced from the second vertical plane by a dimension which is smaller than the inner diameter of the inlet opening (4.1) of the drain pipe bend, characterized in that the lower end (10.1) of the guide channel is oriented in such a way that the central axis of the guide channel at the mouth of the lower end (10.1) is not more than 45° offset, preferably not more than 30° offset, particularly preferably not more than 15° offset relative to the first vertical plane defined by the front box wall (9. 1) or runs parallel to this first plane, and in that the WC connection device is provided with an installation set which comprises the water supply line to be introduced into the guide channel, the water supply line being longer than the guide channel by at least 15%, preferably at least 25%, particularly preferably at least 30%.