In a probe device including a light irradiating portion irradiating a light to a surface of a living body, and a light detecting portion detecting the light passing through an inner portion of the living body so as to emit from the surface of the living body, the probe device is provided with a sheet-like probe holding body, a plurality of light emitting probes and a plurality of detection probes which are attached to the probe holding body at a predetermined interval, a board holding portion attached to a predetermined position of the probe holding portion, an electronic board attached to the board holding portion, a sheet holding portion holding the probe holding body at a predetermined position of a head portion (a tested position) of the test subject, and a fixing band portion for installing the sheet holding portion to the test subject.