Two sets of TACs are simultaneously operated by a start pulse, one set of TACs using a photoelectron pulse due to an excited light from a sample as a stop pulse, and the other set of TACs using a photoelectron pulse due to a fluorescence from the sample as a stop pulse. Each TAC outputs a voltage proportional to the time from the start of action to the receiving of the stop pulse and an excitation light shape and a luminescence transient shape are simultaneously measured on the basis of output voltages from the TACs. A variable offset voltage is added to an output of at least one of the two sets of TACs and the excitation light shape and the luminescence transient shape are displayed on a two-picture synthetic display.