To provide analyzer and analytical method for improving efficiency in concentration analysis of substance in a liquid sample.

This concentration analyzer of substance in liquid includes: a laser irradiation part 1 to produce pulse laser beam 51 which will generate fluorescence if being irradiated on the liquid sample; and a tubular liquid core optical fiber 30 designed so as to be freely curved and allow the liquid sample to circulate inside, through which the pulse laser beam 51 permeates. This analyzer also includes: an optical filter 35 for selectively transmitting wavelength component of the fluorescence generated during penetration through the liquid sample among all outgoing lights 55; a photodetection part 41 for detecting any fluorescence penetrated through the optical filter 35; and an analysis section 45 which quantitatively analyzes concentration of the analyzing object contained in the liquid sample, based on wavelength and intensity of the above fluorescence detected by the photodetection part 41.