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 includes: 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 lights in such a way that the split lights interfere with each other； a lens (140) into which each split lights 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).
