This paper presents a study of the Matteucci effect of a Co-Fe-Si-B amorphous alloy tip used for magnetic recording with a scanning tunneling microscope (STM). The Matteucci effect is a phenomenon in which a pulse-shaped alternating current (ac) voltage is induced between the ends of a torsionally stressed magnetostrictive wire when the magnetization of the core domain is switched by application of an external ac magnetic field parallel to the wire axis. The influence on the tip-to medium spacing using the above tip is investigated experimentally. Quantitative results for various coil currents and frequencies are obtained. The observed Matteucci pulse voltage is less than 10% of the bias voltage of the STM, and the Matteucci pulse width is approximately 1 mus. The influence of the Matteucci effect on the feedback system of the STM is also discussed.