A successive approximation (SAR) analog-to-digital converter for generating a digital signal of N bits is provided. The converter includes a capacitive digital-to-analog conversion circuit including an (N−1)-th conversion unit to a first conversion unit. Each of the first conversion unit to the (N−2)-th conversion unit includes a capacitor. The (N−1)-th conversion unit comprises a number of sub-capacitors. Each of the sub-capacitors of the (N−1)-th conversion unit has substantially the same capacitance with corresponding capacitor of the first conversion unit to the (N−2)-th conversion unit. During the conversion process, the SAR control circuit, after generating the value of the most significant bit (MSB) of the digital signal, generates the value of the next bit by controlling the (N−1)-th conversion unit. Then, the SAR control circuit repeatedly uses at least one of the sub-capacitors of the (N−1)-th conversion unit to generate the value of other bits to perform self linear compensation.