A biological information acquisition apparatus and a biological information acquisition method, both capable of radiating a uniform and efficient light to the whole living body tissue as an object of the detection are provided. The biological information acquisition apparatus of the present invention includes a light source and an acoustic wave detector detecting an acoustic wave generated by making a light from the light source enter the object through an object holding member. Furthermore, one or more light transmitting members are provided, and the light enters the light transmitting member from a side surface side of the acoustic wave detector, and enters the object holding member through the light transmitting member at an angle other than one perpendicular to the object holding member.