Device for magnetically detecting microscopic biological objects comprising: - a microfluidic channel extending between a first upstream end (ex1) and a second downstream end (ex2), the microfluidic channel having an inlet suited for a fluid (Af) on the side of its first upstream end (ex1) and an outlet suited for a fluid (Sf) on the side of its second downstream end (ex2), 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 (C1); - a second magnetic sensor (C2) opposite the first magnetic sensor (C1) 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 (C3) 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 (C4) 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 (ex1) and a second downstream end (ex2), the microfluidic channel having an inlet suited for a fluid (Af) on the side of its first upstream end (ex1) and an outlet suited for a fluid (Sf) on the side of its second downstream end (ex2), 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 (C1); - a second magnetic sensor (C2) opposite the first magnetic sensor (C1) 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 (C3) 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 (C4) 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. <EOS>