A particle component analyzing apparatus and method using a microwave induced plasma to perform element analysis of particles, such as particles existing in a clean room; wherein an aspirator scans a filter to draw particles collected on the filter, and using the microwaves to excite the drawn particles to cause generation of an emission spectrum having a plurality of wavelengths indicative of the elements of the particle, which are measured by a plurality of monochrometers, and converted by an optoelectric converter into electrical signals to identify the different elements in the particle. The invention uses means for obtaining the cube roots of the outputs from the optoelectric converter. By obtaining the ratio of cube root outputs corresponding to the diameters of particles preprocessed into spherical shape of a reference element and of an element to be measured, and then by obtaining the cube root of an output from an element in a measurement sample and by multiplying it by the ratio of cube roots with respect to the reference element, there is obtained an equivalent particle diameter corrected for differences in sensitivity between the elements. Means are provided for determining the composition of a particle from the emission spectrum and for calculating the composition ratios of a plurality of elements from the different emission intensities.