  We show that the hadron-quark mixed phase is restricted to narrow range of
baryon chemical potential by the charge screening effect.
  Accordingly the mixed phase expected in hadron-quark hybrid stars should be
narrow. Although the screening would not have large effect in bulk properties
of the star such as mass or radius, it change the internal structure of the
star very much, which may be tested by the cooling curve, glitch phenomena or
gravitational waves.
