This present invention relates to a voltage converting apparatus with auto-adjusting boost-multiple, which includes a microprocessor unit, a boost multiple control unit, a boost unit, and a voltage converting unit. According to the digital signal, the microprocessor unit generates an output voltage information and a converting multiple information. According to the output voltage information, the boost multiple control unit computes the corresponding relation between an output voltage and an input voltage in order to generate the boost multiple information. Based on the boost multiple information, the boost unit can amplify the output voltage to generate an converting operation voltage. The voltage converting unit operates between the converting operation voltage and a fist voltage, and converts a reference voltage into the output voltage according to the converting multiple information.