PROBLEM TO BE SOLVED: To provide a Doppler sensor that can appropriately take a measurement concerning urination.SOLUTION: The Doppler sensor 1 used for measurement concerning urine discharged from ostium urethrae externum toward the outside of a body includes: a casing 10 having a structure capable of mounted to a finger a transmission part 11 arranged on the casing 10 which transmits wave energy from the side different from the side of the finger mounted on the casing 10 and a receiving part 12 arranged on the casing which receives a reflection wave of the wave energy transmitted by the transmission part 11 at the side different from the side of the finger mounted on the casing 10.
