The invention relates to a method and apparatus for linearizing a flow velocity sensor based on pressure difference measurement. According to the method, such a difference of two pressure signals (4, 5) is measured from the flow under measurement that is proportional to the square of the flow velocity, the difference of said two pressure signals (4, 5) is measured using a micromechanically manufactured symmetrical capacitive differential pressure sensor (20) based on the force balance principle, in which sensor the pressure-induced deviation from force balance is compensated for by inducing on the pressure-sensing diaphragm (23) of said differential pressure sensor (20) a force-balance-restoring electrostatic pressure so that the pressure-sensing diaphragm (23) is subjected to the force-balance-restoring electrostatic force, whereby the amplitude of the force-balance-restoring electrical feedback control signal, which also acts as the system output signal, is directly proportional to the square root of said difference of said two pressure signals, and thus, a linear function of the flow velocity. According to the invention, said feedback control voltage depending on the direction of the pressure difference is applied only to either of the stationary electrodes (21 or 22) disposed on the same side relative to the sensing diaphragm so that the electrostatic force of attraction thus induced acts counter to the force generated by the pressure difference under measurement, whereby the polarity of the system output voltage signal is dependent on the direction of the flow.