A chamber-status monitoring apparatus includes a plurality of chambers, a time-division multiplexer configured to receive, via optical fiber probes, optical signals from each chamber, to divide each optical signal into first time slots having a predetermined duration, and to multiplex the first time slots to generate an OTDM signal, a multi-input optical emission spectroscope configured to receive and disperse the OTDM signal according to wavelengths to measure spectrum information, and a controller configured to divide the spectrum information of the dispersed OTDM signal into second time slots with a predetermined time interval therebetween, to classify the second time slots according to the chambers to obtain spectrum information of the optical signals of the individual chambers, and to control endpoint detection in each of the chambers in accordance with the spectrum information of the optical signal of the corresponding chamber.