This invention relates to an analytical method and a relevant equipment for particulate substances in a sample with the detection of acoustic waves generated in the sample with the irradiation of onto the sample. In this invention, the light power density of the irradiating light onto the sample is set high enough above the breakdown threshold of the particulate substances in the sample, and low enough below the breakdown threshold of the media, and the particulate substances in the sample are counted by detecting the acoustic waves generated by the breakdown of the particulate substances. The particulate substances are also analyzed for their components on the basis of the light signal (emission spectrum) which is detected with a dispersed spectrum from the light which is generated by the breakdown of the particulate substances.