The present invention is to present a sample analyzer capable of automatically stabilizing the laser diode in multi-mode oscillation. A sample analyzer 1 comprises: a laser diode (LD) 501d for irradiating a sample with laser light; a photodiode (PD) 501e for detecting amount of light emitted from the LD 501d; a APC circuit 501b for outputting a direct current to be supplied to the LD 501d such that the amount of light emitted from the LD 501d is maintained at a predetermined amount, based on the amount of light detected by the PD 501e; a high frequency oscillation circuit 501f for superimposing a high frequency component on the direct current outputted from the APC circuit 501b; and a high frequency automatic adjustment circuit 501c for controlling amplitude of the high frequency component outputted from the high frequency oscillation circuit 501f according to magnitude of the direct current outputted from the APC circuit 501b such that the LD 501d oscillates in a multi-mode.