This invention may measure the sprayed particle sprayed from the nozzle safely with the use of a conventional particle size distribution measuring device The particle size distribution measuring device may measure particle size distribution of a particle group, and may include a device body comprising a light source that irradiates light on the particle group and a light detector that detects intensity of diffracted light or/and scattered light generated by irradiation of the light, a spray measuring system that introduces a sprayed particle group as being the particle group sprayed from a nozzle into a measuring area between the light source and the light detector, and an ordinary measuring system that arranges a measuring cell that accommodates an ordinary particle group as being a particle group other than the sprayed particle group between the light source and the light detector are arranged to be exchangeable for each other.