Provided is an object information acquiring apparatus including: detecting elements converting an acoustic wave propagated from an object to an electric signal, a processing unit acquiring characteristic information of the object using the electric signal, a supporting unit supporting the detecting elements, an input unit receiving information concerning three-dimensional region of interest, a display controlling unit displaying a predetermined three-dimensional shape representing, a scanning region setting unit setting a scanning region, and a scanning unit moving the supporting unit, wherein the display controlling unit changes the size of the region of interest stepwise by using a feature value peculiar to the apparatus as a unit based on the inputted information, and displays the changed region of interest.
