An object information acquiring apparatus is used, including: an optical transmission system for transmitting light from a light source; a photoacoustic probe including an irradiating end for irradiating an object with light and a receiver for receiving acoustic waves generated from the object that has been irradiated with light; a processor for acquiring information on the object based on the acoustic waves; a light quantity meter for measuring the quantity of light emitted from the irradiating end; a memory for storing a measurement value; and a presentation unit. The processor compares the measurement value with a reference value of light quantity or a history of measurement value stored in the memory, and provides a result regarding whether or not the measurement value is within a reference range to the presentation unit.