Abstract: A subject information detecting unit I1 includes a sensor mount I21, having an opening I22 at a portion to be in contact with a subject I91 and an internal cavity I23 communicated with the opening I22, the cavity defining a closed spatial structure in a state where the subject information detecting unit I1 is mounted on the subject such that the opening I22 faces the subject I91; a sensor I31 disposed on the sensor mount I21 and receiving pressure information deriving from pulsating signals in a blood vessel I92 in the subject I91, the sensor detecting the pulsating signals in the blood vessel in the subject; and a film member I11 separating the opening I22 from the sensor I31 and blocking the permeation of moisture. The sensor I31 detects the pressure information deriving from pulsating signals from the blood vessel I92 in the subject I91 and propagating through the opening I22, the cavity I23 and the film member I11.