  COMET is a leading experiment to search for coherent conversion of $\mu^-
\mathrm{N}\to e^- \mathrm{N}$ with a high-intensity pulsed muon beamline,
produced by the innovative slow extraction techniques. Therefore, it is
critical to measure the characteristics of the muon beam. We set up a Muon Beam
Monitor (MBM), where scintillation fibers (SciFi) weaved in the cross shape are
coupled to silicon photomultipliers (SiPM), to measure the spatial profile and
timing structure of the extracted muon beam for COMET. The MBM detector has
been tested successfully with a proton beamline in China Spallation Neutron
Source (CSNS) and taken data with good performance in the commissioning run
called COMET Phase-$\alpha$. Experience of the MBM development, such as the
mechanical structure and electronics readout, and its beam measurement results
will be shared.
