An inspection device configured to conduct an inspection of a predetermined inspection object portion (5, SP) in a PTP sheet or in a portion that eventually forms the PTP sheet in a manufacturing process of the PTP sheet configured such that a content is contained in a pocket portion formed in a container film and a cover film is bonded to the container film to close the pocket portion, the inspection device comprising: an irradiator configured to irradiate at least the inspection object portion (5, SP) with predetermined light; an imaging unit configured to take an image of the inspection object portion (5, SP) irradiated with the light emitted from the irradiator; a quality judgment unit configured to detect presence or absence of a defect in the inspection object portion (5, SP) from the image taken by the imaging unit by using a predetermined luminance threshold value (δx1, δx2, δy) and thereby judge the inspection object portion (5, SP) as non-defective or defective; a verification image generating unit configured to generate a verification image with a virtual defective image placed in a non-defective image that is judged as non-defective by the quality judgment unit; and a threshold value verifying unit configured to cause the quality judgment unit to judge the inspection object portion (5, SP) as non-defective or defective by using the verification image, in place of the image taken by the imaging unit and to verify the luminance threshold value (δx1, 6x2, δy), based on a result of the judgement, wherein: the irradiator is configured to radiate lights of multiple different wavelength components, which include near-infrared light, red color light, blue color light and green color light, and a luminance of the defective image is set independently according to the light of each of the wavelength components, based on a luminance of a portion of the non-defective image, which is taken corresponding to each of the multiple different wavelength components and in which the defective image is placed. an irradiator configured to irradiate at least the inspection object portion (5, SP) with predetermined light; an imaging unit configured to take an image of the inspection object portion (5, SP) irradiated with the light emitted from the irradiator; a quality judgment unit configured to detect presence or absence of a defect in the inspection object portion (5, SP) from the image taken by the imaging unit by using a predetermined luminance threshold value (δx1, δx2, δy) and thereby judge the inspection object portion (5, SP) as non-defective or defective; a verification image generating unit configured to generate a verification image with a virtual defective image placed in a non-defective image that is judged as non-defective by the quality judgment unit; and a threshold value verifying unit configured to cause the quality judgment unit to judge the inspection object portion (5, SP) as non-defective or defective by using the verification image, in place of the image taken by the imaging unit and to verify the luminance threshold value (δx1, 6x2, δy), based on a result of the judgement, wherein: the irradiator is configured to radiate lights of multiple different wavelength components, which include near-infrared light, red color light, blue color light and green color light, and a luminance of the defective image is set independently according to the light of each of the wavelength components, based on a luminance of a portion of the non-defective image, which is taken corresponding to each of the multiple different wavelength components and in which the defective image is placed. the irradiator is configured to radiate lights of multiple different wavelength components, which include near-infrared light, red color light, blue color light and green color light, and a luminance of the defective image is set independently according to the light of each of the wavelength components, based on a luminance of a portion of the non-defective image, which is taken corresponding to each of the multiple different wavelength components and in which the defective image is placed.