The objective of the invention is to make it possible to provide a high-resolution photoacoustic imaging device at low cost. This photoacoustic wave detecting device is provided with: a beam splitter (111) which splits emitted light from a light source； an optical physical property shifting unit (120) which changes at least one physical property of the split beams in such a way that the split beams interfere with one another； a lens (140) into which each split beams enters parallel to the optical axis； and an acoustic detecting unit (150) which detects an acoustic wave generated in a region of an observation target at the focal point of the lens (140).
