A detection circuit for accurately detecting a very small foreign material and an inspection/measurement device using the same are provided. The inspection/measurement device includes: an irradiation section that irradiates a laser beam to a surface of a specimen; and a detection section that detects scattered light from the surface of the specimen and generates a detection signal. The detection section includes: a photon counting sensor that outputs M output signals from photo-detecting elements of N pixels (M and N are natural numbers, and M