  We present a magnetic field mapping of water maser clouds in the star-forming
region W3 IRS5, which has been made on the basis of the linear polarization
VLBI observation. Using the Very Long Baseline Array (VLBA) at 22.2 GHz, 16 of
61 detected water masers were found to be linearly polarized with polarization
degrees up to 13%. Although 10 polarized features were widely distributed in
the whole W3 IRS5 water maser region, they had similar position angles of the
magnetic field vectors (~75 deg from the north). The magnetic field vectors are
roughly perpendicular to the spatial alignments of the maser features. They are
consistent with the hourglass model of the magnetic field, which was previously
proposed to explain the magnetic field in the whole W3 Main region (r~0.1 pc).
They are, on the other hand, not aligned to the directions of maser feature
proper motions observed previously. This implies that the W3 IRS5 magnetic
field was controlled by a collapse of the W3 Main molecular cloud rather than
the outflow originated from W3 IRS5.
