The authors investigated the Verwey transition in field-emitted electrons from a << 110 >>-oriented magnetite whisker by means of temperature and emission-current-controlled spin-polarization measurements. Under a condition of total emission current of 1.5 nA, which is relatively high within the measured range, the spin polarization began to increase around 100 K due to the Verwey transition. At the low-temperature region, the spin polarization was sensitive to the emission current and the energy. Therefore, it is suggested that t(2g) band of Fe3O4 at the surface becomes narrower and possesses lower energy than that in an ideal bulky condition.