Direction of the interplanetary magnetic field (IMF) which governs the orientation of the Halley's magnetosphere was restored by using Giotto magnetic field data. The Giotto trajectory was a twisted curve in the coordinate system rotating with IMF vector and covered rather uniformly the transverse cross section of the comet. Magnetic field vectors show a regular structure arising from the field line draping about the cometary ionosphere. Violations of the field line draping occur only at the moments of rapid changes of IMF orientation. ¿ American Geophysical Union 1994