195Pt Knight shift (KS) measurements covering the superconducting multiple phases for major field ( H) orientations have been carried out on the high-quality single crystal UPt3. For H>5 kOe, the KS does not change below the superconducting transition temperature Tc down to 28 mK, regardless of major crystal orientations, which provides evidence that the odd-parity superconductivity with the parallel spin pairing is realized. By contrast, the KS decreases below Tc for Hb∥b axis and Hb<5 kOe and for Hc∥c axis and Hc<2.3 kOe, whereas the KS for Ha∥a axis is T independent across Tc down to Ha∼1.764 kOe. These novel findings entitle UPt3 as the first spin-triplet odd-parity superconductor including a nonunitary pairing characterized by the two-component d vector like db+idc at low T and low H.