A human detection system 18 includes: a camera 19 that acquires detection image data Dd of a detection region D, the detection region D being a prescribed region including a portion of a crane 1; a deviation determination unit 21c in which image data of the crane 1 included in the detection image data Dd acquired by the camera 19 in a state of being disposed at a reference position is set as reference image data Sd of the detection region D, and in which the detection image data Dd of the detection region D acquired at an arbitrary time by the camera 19 is compared to the reference image data Sd to determine whether the position of the camera 19 has deviated from the reference position; and a reporting unit 21d that reports that the position of the camera 19 has deviated.