  We present H-alpha velocity fields of thirteen giant H II regions in four
nearby dwarf irregular galaxies, NGC 2366, Holmberg II, IC 2574, and WLM. We
classify the velocity features as well as the morphologies of the H II regions.
The H-alpha velocity features are divided into three categories; three H II
regions show chaotic feature with a typical scale of variation of a few 100 pc
in size and a few 10 km s^{-1} in velocity, one shows expanding-bubble feature,
and the remaining nine have calm velocity fields. There is a correlation
between the H-alpha velocity feature and the morphology of H II regions. We
measured bulk motion of the H II regions relative to the ambient H I velocity
for the H II regions with calm velocity fields and found a typical velocity
difference of about 5 km s^{-1}. We discuss a model for origin of star-forming
regions based on the presence of the velocity difference between H-alpha and H
I gas as well as the H I characteristics.
