Dew point measuring device for measuring a dew point of a process fluid which flows in a dehumidifying plant for dehumidifying plastics in granular and/or microgranular and/or powder and/or flake form, said plant comprising a process fluid generator and at least one dehumidifying hopper intended for supplying a respective user machine; wherein said dew point measuring device comprises: process fluid extracting means (6, 6', 6"), which is configured for extracting from said dehumidifying plant a quantity of process fluid and is arranged in an extraction conduit included in said dehumidifying plant and positioned immediately downstream, with respect to an advancement direction of said process fluid in said dehumidifying plant, of a mixing zone between a process fluid exiting said process fluid generator and a process fluid exiting said at least one dehumidifying hopper; and processing means, in flowing communication with said process fluid extracting means (6, 6', 6") for receiving from said process fluid extracting means (6, 6', 6") said quantity of process fluid and determining a dew point value of said quantity of process fluid; wherein said process fluid extracting means comprises at least one process fluid extracting tubular element (6, 6', 6") projecting inwards said extraction conduit and provided with a plurality of process fluid extracting holes, each of them for extracting a determined quantity of said process fluid from a respective inner zone of said extraction conduit, said at least one process fluid extracting tubular element (6, 6', 6") mixing internally said determined quantities of said process fluid extracted by said process fluid extracting holes and sending a mixture of said determined quantities of said process fluid to said processing means; said dew point measuring device is characterized in that it comprises at least two of said process fluid extracting tubular elements (6, 6', 6") each extending along a respective axis (R', R") of prevalent extent; wherein said respective axes (R', R") of prevalent extent lie on respective planes positioned in sequence transversely, in particular perpendicularly, to said advancement direction of said process fluid; or wherein said axes (R', R") of prevalent extent are positioned on a same plane positioned transversely, in particular perpendicularly, to said advancement direction of said process fluid; wherein said axes (R', R") of prevalent extent are angularly staggered in relation to one another by an angle (β) that is less than 180°, in particular substantially the same as 90°, or wherein said axes (R', R") of prevalent extent are aligned on one another. process fluid extracting means (6, 6', 6"), which is configured for extracting from said dehumidifying plant a quantity of process fluid and is arranged in an extraction conduit included in said dehumidifying plant and positioned immediately downstream, with respect to an advancement direction of said process fluid in said dehumidifying plant, of a mixing zone between a process fluid exiting said process fluid generator and a process fluid exiting said at least one dehumidifying hopper; and processing means, in flowing communication with said process fluid extracting means (6, 6', 6") for receiving from said process fluid extracting means (6, 6', 6") said quantity of process fluid and determining a dew point value of said quantity of process fluid; wherein said process fluid extracting means comprises at least one process fluid extracting tubular element (6, 6', 6") projecting inwards said extraction conduit and provided with a plurality of process fluid extracting holes, each of them for extracting a determined quantity of said process fluid from a respective inner zone of said extraction conduit, said at least one process fluid extracting tubular element (6, 6', 6") mixing internally said determined quantities of said process fluid extracted by said process fluid extracting holes and sending a mixture of said determined quantities of said process fluid to said processing means; said dew point measuring device is characterized in that it comprises at least two of said process fluid extracting tubular elements (6, 6', 6") each extending along a respective axis (R', R") of prevalent extent; wherein said respective axes (R', R") of prevalent extent lie on respective planes positioned in sequence transversely, in particular perpendicularly, to said advancement direction of said process fluid; or wherein said axes (R', R") of prevalent extent are positioned on a same plane positioned transversely, in particular perpendicularly, to said advancement direction of said process fluid; wherein said axes (R', R") of prevalent extent are angularly staggered in relation to one another by an angle (β) that is less than 180°, in particular substantially the same as 90°, or wherein said axes (R', R") of prevalent extent are aligned on one another.