Disclosed are a continuous-time delta-sigma analog-to-digital converter and an operation method thereof. More particularly, a continuous-time delta-sigma analog-to-digital converter, including: a linear integrator configured to generate a first output signal corresponding to a preset input voltage based on an operation of a linear Gm circuit that receives the preset input voltage; and a quantizer configured to generate a second output signal corresponding to the first output signal based on an operation of a body-driven VCO that receives the first output signal and to generate a digital output code corresponding to the second output signal based on an operation of a Frequency to Digital Converter (FDC) that receives the second output signal is disclosed.