  In the standard model extended by a single complex scalar boson with a softly
broken global U(1) symmetry, a pseudo Nambu-Goldstone boson becomes a candidate
for dark matter. In this paper, we discuss the direct detection of the pseudo
Nambu-Goldstone boson dark matter. Since the tree-level amplitude for dark
matter-nucleon scattering vanishes, higher order quantum corrections for the
amplitude should be taken into account. We perform the calculation at the
next-to-leading order in QCD in a systematic manner.
