An image information obtaining apparatus having: a light source; a transducer which detects an acoustic wave and converts the acoustic wave to an electrical signal; a signal processing unit which generates image data, using the electrical signal; and a memory unit which stores a reference acoustic signal produced by the transducer detecting an acoustic wave generated when light is irradiated from the light source onto a phantom having acoustic parameters and optical parameters substantially the same as an object and converting the acoustic wave to an electrical signal, wherein the transducer produces an object acoustic signal by converting the acoustic wave, generated when light is irradiated onto an object from the light source, to an electrical signal; and the signal processing unit subtracts the reference acoustic signal from the object acoustic signal and generates image data from the signal resulting from this subtraction.