An optical line monitoring apparatus, including: a group information recording portion which records group information about to which splitter respective terminators are connected; a normal information recording portion which records intensities of reflected lights from a plurality of terminators in a state in which a failure is not occurring in optical lines; a monitored information recording portion which records intensities of reflected lights from the plurality of terminators in failure monitoring time; an attenuation amount determination portion which determines a terminator the reflected light intensity of which is attenuated compared with the corresponding reflected light intensity in normal information; and a control portion which determines, if the intensities of the reflected lights of all the terminators connected to the same splitter are attenuated by the same value, that a failure has occurred between the test apparatus and the splitter to which all the terminators are connected.