This paper discusses single-event effect (SEE) on SiGe heterojunction bipolar transistors (SiGe HBTs) using laser microbeam irradiation test. Our work observes the sensitive volume in SiGe HBTs, and measures the transient current and charge collection of the collector for different voltage and different laser energy. Then, the experimental phenomena are analyzed according to the device structure. The results show that SiGe HBTs are susceptible to SEE, the 1064 nm laser of about 1.5 nJ energy causes SEE by transient current. The region within collector/substrate (C/S) junction is the sensitive volume of the domestic SiGe HBTs. As the incident laser energy enhances, the current pulse increases, and the amount of charge collection rises. The crest of the current pulse increases when the applied voltage is increased. SiGe HBT single-event effect is affected by both voltage and laser energy. Applied voltage mainly affects the peak of transient current; however, charge collection is strongly dependent on the energy of incident laser.