A sample analyzer, comprising: a laser diode for irradiating a sample with laser light; a light amount detector for detecting amount of light emitted from the laser diode; a direct current output part for outputting a direct current to be supplied to the laser diode such that the amount of light emitted from the laser diode is maintained at a predetermined amount, based on the amount of light detected by the light amount detector; a high frequency superimposing part (501f, 501g) for superimposing a high frequency component on the direct current outputted from the direct current output part; and a high frequency control part for controlling amplitude of the high frequency component outputted from the high frequency superimposing part (501f, 501g) according to magnitude of the direct current outputted from the direct current output part such that the laser diode oscillates in a multi-mode, characterised in that the high frequency control part executes an initial drive control for controlling the high frequency superimposing part (501f, 501g) so as not to superimpose the high frequency component on the direct current outputted from the direct current output part, and thereafter executes a multi-mode oscillation control for controlling the high frequency superimposing part (501f, 501g) so as to superimpose the high frequency component on the direct current outputted from the direct current output part such that the laser diode oscillates in the multi-mode; and the high frequency control part determines a standard current value based on current value of the direct current outputted from the direct current output part while executing the initial drive control, and controls the high frequency superimposing part (501f, 501g) such that the current value of the direct current outputted from the direct current output part approaches the standard value while executing the multi-mode oscillation control. a laser diode for irradiating a sample with laser light; a light amount detector for detecting amount of light emitted from the laser diode; a direct current output part for outputting a direct current to be supplied to the laser diode such that the amount of light emitted from the laser diode is maintained at a predetermined amount, based on the amount of light detected by the light amount detector; a high frequency superimposing part (501f, 501g) for superimposing a high frequency component on the direct current outputted from the direct current output part; and a high frequency control part for controlling amplitude of the high frequency component outputted from the high frequency superimposing part (501f, 501g) according to magnitude of the direct current outputted from the direct current output part such that the laser diode oscillates in a multi-mode, characterised in that the high frequency control part executes an initial drive control for controlling the high frequency superimposing part (501f, 501g) so as not to superimpose the high frequency component on the direct current outputted from the direct current output part, and thereafter executes a multi-mode oscillation control for controlling the high frequency superimposing part (501f, 501g) so as to superimpose the high frequency component on the direct current outputted from the direct current output part such that the laser diode oscillates in the multi-mode; and the high frequency control part determines a standard current value based on current value of the direct current outputted from the direct current output part while executing the initial drive control, and controls the high frequency superimposing part (501f, 501g) such that the current value of the direct current outputted from the direct current output part approaches the standard value while executing the multi-mode oscillation control.