The present invention discloses a successive approximation analog-to-digital converter capable of improving the accuracy of analog-to-digital conversion. An embodiment of this converter comprises: a successive approximation analog-to-digital converting circuit operable to generate M bits according to an analog input signal in which the M bits include a most significant bit (MSB) and successive M−1 bit(s) in succession to the MSB while the number M is an integer greater than one; and a multi-bit generating circuit operable to receive a capacitor array output signal and a comparison signal outputted from the successive approximation analog-to-digital converting circuit for a predetermined time after the generation of the M bits, and then generate N bits at a time accordingly in which the N bits include a least significant bit (LSB) and successive N−1 bit(s) ahead of the LSB while the number N is an integer greater than one.