Device (4, 5) for magnetically detecting microscopic biological objects comprising: - a microfluidic channel extending between a first upstream end and a second downstream end, the microfluidic channel having an inlet suited for a fluid (Af) on the side of its first upstream end and an outlet suited for a fluid (Sf) on the side of its second downstream end, the microfluidic channel having a length in a first direction ( x) of flow, a width in a second direction ( y) perpendicular to the first direction ( x) and a height in a third direction ( z) perpendicular to the first and second directions ( x, y); - a plurality of magnetic sensors (C1, C2,..., Cn) arranged against an inner wall of the microfluidic channel; and - a permanent magnet arranged against an outer wall of the microfluidic channel, in such a way that the plurality of magnetic sensors (C1, C2,..., Cn) is immersed in a magnetic field created by the permanent magnet; the plurality of magnetic sensors (C1, C2,..., Cn) comprises: - a first magnetic sensor; - a second magnetic sensor opposite the first magnetic sensor in such a way that the first and second magnetic sensors (C1, C2) are aligned parallel to the third direction ( z); - a third magnetic sensor arranged in such a way that the first and third magnetic sensors (C1, C3) are aligned parallel to the first direction ( x) and/or a fourth magnetic sensor arranged in such a way that the second and fourth magnetic sensors (C2, C4) are aligned parallel to the first direction ( x); the third and fourth magnetic sensors (C3, C4) being arranged downstream of the first and second magnetic sensors (C1, C2); - a data processing system configured to determine a velocity of an object detected from the time elapsed between two detections of a relevant event by two sensors aligned parallel to the first direction ( x) and to determine a height of an object detected from the ratio of the signals emitted by at least one pair of opposite sensors. - a microfluidic channel extending between a first upstream end and a second downstream end, the microfluidic channel having an inlet suited for a fluid (Af) on the side of its first upstream end and an outlet suited for a fluid (Sf) on the side of its second downstream end, the microfluidic channel having a length in a first direction ( x) of flow, a width in a second direction ( y) perpendicular to the first direction ( x) and a height in a third direction ( z) perpendicular to the first and second directions ( x, y); - a plurality of magnetic sensors (C1, C2,..., Cn) arranged against an inner wall of the microfluidic channel; and - a permanent magnet arranged against an outer wall of the microfluidic channel, in such a way that the plurality of magnetic sensors (C1, C2,..., Cn) is immersed in a magnetic field created by the permanent magnet; - a first magnetic sensor; - a second magnetic sensor opposite the first magnetic sensor in such a way that the first and second magnetic sensors (C1, C2) are aligned parallel to the third direction ( z); - a third magnetic sensor arranged in such a way that the first and third magnetic sensors (C1, C3) are aligned parallel to the first direction ( x) and/or a fourth magnetic sensor arranged in such a way that the second and fourth magnetic sensors (C2, C4) are aligned parallel to the first direction ( x); the third and fourth magnetic sensors (C3, C4) being arranged downstream of the first and second magnetic sensors (C1, C2); - a data processing system configured to determine a velocity of an object detected from the time elapsed between two detections of a relevant event by two sensors aligned parallel to the first direction ( x) and to determine a height of an object detected from the ratio of the signals emitted by at least one pair of opposite sensors.