A fluorescence analysis optical multiplexer/demultiplexer, a fluorescence analysis optical module, a fluorescence analyzer, a fluorescence/photothermal conversion spectroscopic analyzer, and a fluorescence analysis chip, according to which LIF analysis can be carried out easily and with high sensitivity, and moreover photothermal conversion spectroscopic analysis can be carried out easily and simultaneously with the LIF analysis. A microchemical system 100 as the fluorescence analyzer is comprised of a fluorescence analysis optical module 100a, a probe 50 that condenses exciting light onto a sample solution in a channel 204 inside a fluorescence analysis chip 20, and a sample stage 21 on which the fluorescence analysis chip 20 is mounted. The fluorescence analysis optical module 100a is comprised of an exciting light source 53 that outputs exciting light of dominant wavelength .lamda..sub.1, a fluorescence analysis optical multiplexer/demultiplexer 56 for use in the fluorescence analyzer which analyzes fluorescence of dominant wavelength .lamda..sub.2 (.lamda..sub.2>.lamda..sub.1) emitted from the sample upon the sample being irradiated with the exciting light via the probe 50, a detector 54 that receives the fluorescence, an optical fiber 106 that connects the fluorescence analysis optical multiplexer/demultiplexer 56 to the exciting light source 53, an optical fiber 107 that connects the fluorescence analysis optical multiplexer/demultiplexer 56 to the probe 50, and an optical fiber 108 that connects the fluorescence analysis optical multiplexer/demultiplexer 56 to the detector 54. The channel 204 through which the sample solution is passed is coated with a reflective metal film 205.