Provided are a leakage light detection device, an imaging device, a leakage light detection method, and a non-transitory computer readable recording medium storing a leakage light detection program capable of improving quality of a captured image. A determination unit (11A) compares a pixel value (Gu3) of a pixel (G12) with a pixel value (Gb1) of a pixel (G14) and determines that the pixel (G12) has leakage light from a pixel (G11) in a case where the pixel value (Gu3) is larger than the pixel value (Gb1) by a threshold (TH) or more, and compares a pixel value (Gd3) of a pixel (G13) with the pixel value (Gb1) of the pixel (G14) and determines that the pixel (G13) has the leakage light from the pixel (G11) in a case where the pixel value (Gd3) is larger than the pixel value (Gb1) by the threshold (TH) or more.