An object information acquiring apparatus is used, which has: a region setter setting a first region and a second region inside an object； a plurality of probes each receiving an acoustic wave propagated from the object to which light is radiated and outputting an electrical signal； a sound speed determiner setting a plurality of sound speeds for the first region and the second region respectively； an imaging processor acquiring an image using an electrical signal for each sound speed of the first region and acquiring an image using an electrical signal for each sound speed of the second region； a characteristic amount acquirer acquiring a comparison characteristic amount in a common region of the first region and the second region for each sound speed.
