The Advanced LIGO's discovery of gravitational-wave events GW150914 and GW151226 has stimulated extensive studies on the origin of binary black holes. Supposing the gravitational-wave events could be explained by binary primordial black hole mergers, the speaker investigated the corresponding stochastic gravitational-wave background and pointed out the possibility to detect this background by the Advanced LIGO in the near future. He used the non-detection of stochastic gravitational-wave background to give a new independent constraint on the abundance of primordial black holes in dark matter. In this talk, the recent results will be presented by the speaker.
