A device (10) for wall-mounting a sanitary fixture installation structure (1) has a wall fastener (11); a locator (12) insertable inside the structure (1); a locking member (13) slidable inside the fastener (11) and having a nut screw portion (56); and an externally threaded connecting rod (14) which extends along an assembly axis (A) and connects the locator (12) to the locking member (13); the locking member (13) has an inner manoeuvring seat (60), which is open along the assembly axis (A) to allow the rod (14) to slide, and is closed at opposite ends, along a transverse axis (B) perpendicular to the assembly axis (A), to only allow the locking member (13) a predetermined amount of travel along the transverse axis (B).