A photoacoustic wave detection device includes a light projection optical system and a photoacoustic wave detection system. The light projection optical system includes: a light source that emits excitation light; an excitation light incident surface that guides the excitation light emitted from the light source to the inside by transmission; an internal reflection surface that reflects the excitation light that has entered through the excitation light incident surface by internal reflection; and a prism having positive refractive power and an excitation light emitting surface for emitting the excitation light reflected by the internal reflection surface to the outside by transmission. The photoacoustic wave detection system includes: the prism; and a transducer that detects a photoacoustic wave that has passed through the excitation light emitting surface of the prism, is reflected by the internal reflection surface, and is emitted from the prism. An optical path from the excitation light emitting surface to the transducer in the photoacoustic wave detection system is filled with a prism glass material including the prism.