The invention provides a sound processing device. In one embodiment, the sound processing device comprises a first microphone, a first analog-to-digital converter, a second microphone, and a second analog-to-digital converter. The first microphone detects a first sound pressure to generate a first analog audio signal. The first analog-to-digital converter converts the first analog audio signal from analog to digital to obtain a first digital audio signal. The second microphone detects a second sound pressure to generate a second analog audio signal. The second analog-to-digital converter receives the first digital audio signal and a clock signal, inverts the phase of the first digital audio signal to generate a third digital audio signal, converts the second analog audio signal from analog to digital to obtain a second digital audio signal, encodes a fourth digital audio signal according to the second digital audio signal, outputs data bits of the third digital audio signal when the clock signal oscillates to a logic low level, and outputs data bits of the fourth digital audio signal when the clock signal oscillates to a logic high level.