1. An object detection apparatus for detecting an object to be detected from a frame image, comprising: a window setting unit configured to set a window to be used for detection of the object to be detected in the frame image and acquire a first window image having an image of the window; a pixel value correction unit configured to generate a second window image by acquiring a value smaller than a pixel value of a pixel inside the first window image acquired by the window setting unit when the pixel value is smaller than a correction reference value; a feature amount calculation unit configured to calculate a feature amount of the second window image generated by the pixel value correction unit; a used image determination unit configured to determine whether or not to use the second window image for calculation of an identification value indicating whether or not the object to be detected is present in the window on the basis of the feature amount calculated by the feature amount calculation unit; and an identification value calculation unit configured to calculate the identification value indicating a degree of presence of the object to be detected inside the second window image by using feature data of the object to be detected when the used image determination unit determines to use the second window image.