We apply muon spin relaxation (μSR) technique to study the magnetic behaviors of the photosensitive molecular magnet. 1:1 complexes of bis(hexafluoroacetylacetonate) manganese(II), {Mn(hfac)2} with diazodi(4-pyridyl)methane as a photoresponsible magnetic coupler. The μSR time spectra have been collected before and after laser irradiation as a function of temperature from 290 K to 10 K and as a function of irradiation time during 30 hours. While we are not successful in detecting meaningful effects of irradiation at the present stage, we discuss potential usability of μSR technique to reveal the expected unconventional feature of the photo- induced magnetic order.