Disclosed is a series-parallel type analog-to-digital converter having an analog signal first digitized through coarse quantization to thereby obtain a high-order converted code, and then, the quantization error of the high-order converted code digitized to thereby obtain a low-order converted code, in which it is adapted such that low-order converted codes are sequentially classified into three groups, and when a specific group is output as a redundancy code, a correction code for correcting the high-order converted code is output from the low-order encoder providing the converted code of that group.