General expression for the noncoplanar component of the magnetic field in the front of the quasi-perpendicular fast collisionless shock is derived from the two-fluid hydrodynamics in the assumptions of (1) stationarity, (2) one-dimensionality, and (3) quasi-neutrality of the shock. The tensorial structure of ion and electron pressure is taken into account. Limits of validity of previously proposed phenomenological expressions are found. ¿ American Geophysical Union 1996