A MEMS triaxial magnetic sensor device, provided with a sensing structure comprising: a substrate; an outer frame, internally defining a window and elastically coupled to first anchorages fixed with respect to said substrate by means of first elastic elements; a mobile structure, arranged in the window suspended above said substrate, elastically coupled to said outer frame by means of second elastic elements, and carrying a conductive path for flow of an electric current; and an elastic arrangement (22, 24), within said window, operatively coupled to said mobile structure, wherein said mobile structure is configured to perform, due to said first and second elastic elements and of said elastic arrangement (22, 24): a first sensing movement in response to Lorentz forces (F L) originating from a first magnetic-field component (B x) directed parallel to a first horizontal axis (x) defining a first sensing axis; a second sensing movement in response to Lorentz forces (F L) originating from a second magnetic-field component (B y) directed parallel to a second horizontal axis (y) defining a second sensing axis; and a third sensing movement in response to Lorentz forces (F L) originating from a third magnetic-field component (B z) directed parallel to a vertical axis (z) defining a third sensing axis, in the presence of said electric current in said conductive path; said first, second, and third sensing movements being distinct and decoupled from one another and detection along each sensing axis being decoupled from detection along the other sensing axes; characterized in that said sensing structure has a first axis of symmetry parallel to the first horizontal axis (x) and a second axis of symmetry (A') parallel to the second horizontal axis (y), said first (x) and second (y) horizontal axes defining a horizontal plane (xy); wherein said first sensing movement is a movement of rotation of said mobile structure about said second axis of symmetry (A'), fixedly with respect to said outer frame, and is defined by said first elastic elements; said second sensing movement is a movement of rotation of said mobile structure about said first axis of symmetry, decoupled from said outer frame, and is defined by said second elastic elements and said elastic arrangement (22, 24); and said third sensing movement is a movement of translation in said horizontal plane (xy), decoupled from said movements of rotation about said first and second axes of symmetry (A, A') and is defined by said elastic arrangement (22, 24). a substrate; an outer frame, internally defining a window and elastically coupled to first anchorages fixed with respect to said substrate by means of first elastic elements; a mobile structure, arranged in the window suspended above said substrate, elastically coupled to said outer frame by means of second elastic elements, and carrying a conductive path for flow of an electric current; and an elastic arrangement (22, 24), within said window, operatively coupled to said mobile structure, wherein said mobile structure is configured to perform, due to said first and second elastic elements and of said elastic arrangement (22, 24): a first sensing movement in response to Lorentz forces (F L) originating from a first magnetic-field component (B x) directed parallel to a first horizontal axis (x) defining a first sensing axis; a second sensing movement in response to Lorentz forces (F L) originating from a second magnetic-field component (B y) directed parallel to a second horizontal axis (y) defining a second sensing axis; and a third sensing movement in response to Lorentz forces (F L) originating from a third magnetic-field component (B z) directed parallel to a vertical axis (z) defining a third sensing axis, in the presence of said electric current in said conductive path; said first, second, and third sensing movements being distinct and decoupled from one another and detection along each sensing axis being decoupled from detection along the other sensing axes; characterized in that said sensing structure has a first axis of symmetry parallel to the first horizontal axis (x) and a second axis of symmetry (A') parallel to the second horizontal axis (y), said first (x) and second (y) horizontal axes defining a horizontal plane (xy); wherein said first sensing movement is a movement of rotation of said mobile structure about said second axis of symmetry (A'), fixedly with respect to said outer frame, and is defined by said first elastic elements; said second sensing movement is a movement of rotation of said mobile structure about said first axis of symmetry, decoupled from said outer frame, and is defined by said second elastic elements and said elastic arrangement (22, 24); and said third sensing movement is a movement of translation in said horizontal plane (xy), decoupled from said movements of rotation about said first and second axes of symmetry (A, A') and is defined by said elastic arrangement (22, 24).