  Under the hydrostatic pressure $P=1.48$ GPa, polarized neutron elastic
scattering experiments have been carried out on the coupled spin dimer system
TlCuCl$_3$ with the gapped ground state at ambient pressure. Pressure-induced
magnetic ordering occurs at the transition temperature $T_{\rm N}=16.9$ K. As
in the field-induced and impurity-induced magnetic ordered phases, the ordered
moments lie in the $a-c$ plane just below $T_{\rm N}$. An additional spin
reorientation (SR) phase transition was observed at $T_{\rm SR}=10$ K, where
the ordered moments start to incline toward the b-axis. The temperature
variations of the direction and the magnitude of the ordered moments were also
investigated.
