An acoustic wave detector includes: a transducer and a light reflecting member which is positioned between the transducer and a subject surface that is irradiated with the light, and which reflects scattered light on the subject surface. The light reflecting member includes a first reflecting surface and a second reflecting surface positioned closer to the transducer than the first reflecting surface, and a distance between the first reflecting surface and the second reflecting surface is an odd multiple of a half wavelength of a predetermined wavelength included in an acoustic wave generated from the light reflecting member by the scattered light.
