PROBLEM TO BE SOLVED: To expand a light application range of a probe for a photoacoustic measuring instrument.SOLUTION: A probe for a photoacoustic measuring instrument comprises a light sending part for applying light L to a test object, and a photoacoustic wave detection part 52 for detecting a photoacoustic wave emitted from a portion, which has received the application of the light L, of the test object. In this configuration, the light sending part is provided with light propagation means 51 such as an optical fiber for propagating light from a light source, and a light transmission member 55. The light transmission member 55 is formed to have an inner peripheral surface 55a shaped to be a curved concave surface, and an outer peripheral surface 55b shaped to be a curved convex surface with a larger curvature radius than the curvature radius of the inner peripheral surface 55a, the light transmission member 55 being disposed such that the light L emitted from the light propagation means 51 enters the inner peripheral surface 55a.【課題】光音響計測装置用プローブの光照射範囲を拡大する。【解決手段】被検体に向けて光Ｌを照射する送光部と、光Ｌの照射を受けた被検体の部分から発せられた光音響波を検出する光音響波検出部５２とを有してなる光音響計測装置用プローブにおいて、送光部を、光源からの光を伝搬させる光ファイバ等の光伝搬手段５１と、光透過部材５５とを設けて構成する。そして光透過部材５５は、湾曲した凹面状に形成された内周面５５ａおよび、この内周面５５ａの曲率半径よりも大きい曲率半径を有して湾曲した凸面状に形成された外周面５５ｂを有する形状とした上で、光伝搬手段５１から出射した光Ｌが内周面５５ａに入射するように配置する。【選択図】図３
