An apparatus for measuring the temporal correlation of fundamental particles such as photons, neutrons, X-rays or the like, comprising at least one deflector for sweeping the fundamental particles or images thereof in at least one direction, an aperture member having at least two apertures for time-divisionally extracting the swept fundamental particles or the images thereof, multiplication means, such as dynode groups or photomultipliers, for multiplying each of the extracted fundamental particles or the images thereof and a correlator for performing correlating arithmetic operations on the basis of each output signal from the multiplication means.