Particle diameter measuring apparatus

PROBLEM TO BE SOLVED: To provide a particle size measuring device which displays the proportions of the particle number of each particle size fraction to the total particle number in a circular graph.SOLUTION: A particle size measuring device 1 includes a conversion hardware 15 which converts N pieces of analog signals from N pieces of photo detectors to N pieces of digital signals and outputs the N pieces of digital signals, a particle number measuring part 42 which recognizes the passage of particles to be measured through a measurement space on the basis of the N pieces of digital signals from the conversion hardware 15, an output firmware 16 which outputs X pieces of analog signals from X pieces of photo detectors selected from the N pieces of photo detectors, a particle size measuring part 43 which outputs classified particle size fractions of the measured particles passing through the measurement space based on the X pieces of analog signals from the output firmware 16, and a display control part 54 which displays the particle number of each particle size fraction on a display 50. The display control part 54 displays the proportions of the particle number of each particle size fraction to the total particle number in a circular graph.