  The linear polarization degree (referred to the scattering plane, P_r) as a
function of the solar phase angle, {\alpha}, of solar system objects is a good
diagnostic to understand the scattering properties of their surface materials.
We report Pr of Phaethon over a wide range of {\alpha} from 19.1 deg to 114.3
deg in order to better understanding properties of its surface materials. The
derived phase-polarization curve shows that the maximum of P_r, P_max, is
>42.4% at {\alpha} >114.3 deg, a value significantly larger than those of the
moderate albedo asteroids (P_max ~9%). The phase-polarization curve classifies
Phaethon as B-type in the polarimetric taxonomy, being compatible with the
spectral property. We compute the geometric albedo, p_v, of 0.14 +/- 0.04
independently by using an empirical slope-albedo relation, and the derived p_v
is consistent with previous results determined from mid-infrared spectra and
thermophysical modeling. We could not find a fit to the period in our
polarimetric data in the range from 0 up to 7.208 hr (e.g., less than twice the
rotational period) and found significant differences between our P_r during the
2017 approach to the Earth and that of the 2016. These results imply that
Phaethon has a region with different properties for light scattering near its
orbital pole.
