An object detection device includes: a binary difference image generation unit for generating a binary difference image C by binarizing a difference value between a background image B, which is an image as a reference for the absence of a detection target object in the detection area, and a detection target image F which is an image as a detection target to detect a detection target object in the detection area; a binary second derivative image generation unit for generating a binary second derivative image D by binarizing second derivatives of the detection target image F or of a smoothed image F′, obtained by smoothing the detection target image F; and an object detection unit for detecting the detection target object based on a logical product of the binary difference image C and the binary second derivative image D.