  One of the main purposes on physics at the International Linear Collider
(ILC) is to study the property of dark matter such as its mass, spin, and
interactions between the dark matter and particles in the standard model. Among
those, the interaction between dark matter and higgs boson is important,
because, if the dark matter is a weakly interacting massive particle, the
existence of the dark matter is expected to relate to physics of electroweak
symmetry breaking. In addition, the interaction plays an important role at
direct detection experiments of dark matter. In this report, we discuss how
accurately the coupling constant of the interaction can be measured at the ILC
with the center of mass energy less than 500 GeV.
