The study investigates the presence of massive black holes in the Milky Way halo by searching for long-timescale gravitational microlensing events among 78.7 million stars in the Large Magellanic Cloud (LMC) monitored by the Optical Gravitational Lensing Experiment (OGLE) over 20 years. No events with timescales longer than one year were detected. The properties of thirteen microlensing events with timescales shorter than one year are consistent with astrophysical objects in the LMC or the Milky Way disk, ruling out primordial black holes (PBHs) as a dominant source of gravitational waves. The analysis constraints the fraction of dark matter composed of PBHs, finding that compact objects in the mass range from $1.8 \times 10^{-4} \, M_{\odot}$ to $6.3 \, M_{\odot}$ cannot make up more than 1\% of dark matter, and those in the mass range from $1.3 \times 10^{-5} \, M_{\odot}$ to $860 \, M_{\odot}$ cannot make up more than 10\%. These results conclude that PBH mergers are not a significant contributor to the observed black hole merger rates by gravitational wave detectors.The study investigates the presence of massive black holes in the Milky Way halo by searching for long-timescale gravitational microlensing events among 78.7 million stars in the Large Magellanic Cloud (LMC) monitored by the Optical Gravitational Lensing Experiment (OGLE) over 20 years. No events with timescales longer than one year were detected. The properties of thirteen microlensing events with timescales shorter than one year are consistent with astrophysical objects in the LMC or the Milky Way disk, ruling out primordial black holes (PBHs) as a dominant source of gravitational waves. The analysis constraints the fraction of dark matter composed of PBHs, finding that compact objects in the mass range from $1.8 \times 10^{-4} \, M_{\odot}$ to $6.3 \, M_{\odot}$ cannot make up more than 1\% of dark matter, and those in the mass range from $1.3 \times 10^{-5} \, M_{\odot}$ to $860 \, M_{\odot}$ cannot make up more than 10\%. These results conclude that PBH mergers are not a significant contributor to the observed black hole merger rates by gravitational wave detectors.