A double-bed circular knitting machine with device for correcting automatically variations of the distance between the needle cylinder and the dial. The machine comprises a supporting structure (2) which supports, so that it can rotate about its own vertically oriented axis (3), a needle cylinder (4) and a dial (5), which is arranged above and coaxially to the needle cylinder (4). The needle cylinder (4) has, on its lateral surface, a plurality of axial slots (6), each of which accommodates slidingly a needle (7) that can be actuated with an alternating motion along the corresponding axial slot (6) to form knitting. The dial (5) has a plurality of radial slots (10), each of which accommodates slidingly a needle (11) that can be actuated with alternating motion along the corresponding radial slot (10) to form knitting. Means (14) are provided for feeding threads (15) to the needles (7, 11). The machine comprises a device (16) for correcting automatically the variations of the distance between the needle cylinder (4) and the dial (5). The device comprises: means (17) for detecting the tension of n threads (15) fed to the needles (7, 11) of the machine to form knitting; movement means (18), which are connected to the dial (5) and can be actuated to actuate the movement of the dial (5) along its axis (3) with respect to the needle cylinder (4); an actuation and control element (19) of the electronic type, which is functionally connected to the tension detection means (17) and is adapted to actuate the movement means (18) as a function of the tension of the threads (15) detected by the tension detection means (17).