The present invention is applied to an analyzer according to which a sample to be analyzed is moved through a capillary tube in liquid chromatography or capillary-zone electrophoretic method. The capillary tube has a separation zone and a detection zone. The capillary tube in the detection zone has a section in which it can vibrate and both ends of this section are fixed.Analytes of the sample introduced into the analyzer are separated from each other in the separation zone. When each of the separated analytes is led to the area irradiated with beam in the detection zone, the capillary tube in the detection zone vibrates. This vibration phenomenon is brought about by tension fluctuation of the capillary tube caused by intermittent irradiation of the detection zone with an excitation beam and absorption of the excitation beam by the analyte. Concentration of analytes in the sample can be measured by detecting amplitude of the vibration.