Neda, is your Hydrangea already leafed out?
Neda, the best time is when your plant is dormant, either the late fall, or, if you are in an area where the ground does not freeze, even the winter.
You're welcome, Neda. Good luck with the move.
Neda, most plants prefer to be moved just after they are done flowering..usually that is in fall, or like Douglas said,, when dormant..