The invention relates to a rolling bearing device for telescopic masts and a fork carriage for fork lift trucks. A device for adjusting a rolling bearing (3) for the mutual sliding of mast members (2a, 2b, 2c) for supporting the fork carriage (1) of a fork lift truck, comprises a threaded coupling (9, 10) between the inner ring (4) of the rolling bearing (3) and the relative support pin (8), and an actuation member (11) freely rotatable through the support pin (8) and rotatably connected with the inner ring (4). The actuation member (11) can be manoeuvred to rotate the inner ring (4) and varythe axial position of the rolling bearing (3) with respect to the support pin (8) through the threaded coupling (9, 10).