An analog-to-digital conversion device for multiple input signals includes a sample-and-hold amplifier and an analog-to-digital converter for converting an analog signal output from the sample-and-hold amplifier into a digital signal. According to the analog-to-digital conversion device for multiple input signals and a conversion method therefor, even if an input buffer is not provided, the dynamic range of the analog-to-digital converter may be optimally set depending on the input signals, and current consumption may be reduced.