A subject information acquiring apparatus includes a light source configured to radiate optical pulses coded by a predetermined number of pulse streams to a subject, a probe having a converting element configured to receive photoacoustic waves occurring from the subject, and configured to convert the received photoacoustic waves to electrical signals, and an information acquiring unit configured to decode a predetermined number of signals of the electrical signals output from the converting element and acquire characteristic information on the subject based on the decoded electrical signals, wherein the relative positions of the converting element included in the probe and the subject are changed before the radiation of the predetermined number of optical pulse streams completes, and the electrical signals to be decoded are partially redundant before and after the change of the relative positions of the converting element and the subject.
