To solve the problems of large taper and poor surface quality of micro-holes processed by laser direct machining (LDM), this study proposed a laser and backside electrolytic hybrid machining (LEM) method. This method can reduce the taper and remove slags, recast layer and micro-cracks, thus obtaining high-quality micro-holes. In this study, a picosecond pulsed laser was used to drill 304 stainless-steel sheets. The quality of micro-holes is compared between LDM and LEM before and after optimizing the processing parameters; and the effect of electrolytic voltage and power frequency on the quality was studied. The results show that LDM can reduce the defects by optimizing the processing technology. The roundness is drilled by optimized LDM increased by approximately 30.5%; and the taper is reduced by approximately 35.4%. In contrast, LEM can further improve the outlet roundness and reduce the taper, the oxygen content, and inner roughness based on LDM. The taper decreased by approximately 31.6%; the roundness of the hole outlet increased by approximately 14.8%; the oxygen content and roughness of hole wall decreased by approximately 60.1 and 65.4%, respectively. With the increase in electrolytic voltage, the quality of the inner wall becomes better, but the stray corrosion near inlet becomes worse. With the increase in the power supply pulse frequency, the edge and wall texture are more uniform and clearer, and the processing localization is enhanced.