An X-ray inspection device adapted to detect foreign matter in a target object while the target object is conveyed, the X-ray inspection device comprising: an X-ray emission device configured and arranged to emit X-rays at the target object; a conveyor belt including an endless belt rolled around a pair of rollers, a first portion of the conveyor belt configured to travel along a forward route, and a second portion of the conveyor belt configured to travel along a return route; a scintillator unit configured and arranged to optically convert the X-rays emitted by the X-ray emission device into visible light, the scintillator unit extending in a direction that intersects a conveyance direction of the target object; and a photodiode array configured and arranged to detect the visible light optically converted by the scintillator unit and to convert the visible light into an electrical signal, the photodiode array being disposed along a direction in which the scintillator unit extends, characterized in that the X-ray inspection device further comprises a slit member forming a slit that extends in the direction that intersects the conveyance direction, the slit member disposed on an upstream side of the scintillator unit with respect to a direction of X-ray irradiation so that only the X-rays that passed through the slit enter the scintillator unit; wherein the slit member is arranged so that a width of the slit is narrower than a width of the scintillator unit in the conveyance direction of the target object, and that the width of the slit is equal to or wider than half a light-receiving width of the photodiode array in the conveyance direction of the target object, the slit member, the scintillator and the photodiode array are positioned in the stated sequence listed from the top, and are provided between the first portion of the conveyor belt and the second portion of the conveyor belt, and the X-ray emission device is provided above the first portion of the conveyor belt. an X-ray emission device configured and arranged to emit X-rays at the target object; a conveyor belt including an endless belt rolled around a pair of rollers, a first portion of the conveyor belt configured to travel along a forward route, and a second portion of the conveyor belt configured to travel along a return route; a scintillator unit configured and arranged to optically convert the X-rays emitted by the X-ray emission device into visible light, the scintillator unit extending in a direction that intersects a conveyance direction of the target object; and a photodiode array configured and arranged to detect the visible light optically converted by the scintillator unit and to convert the visible light into an electrical signal, the photodiode array being disposed along a direction in which the scintillator unit extends, characterized in that the X-ray inspection device further comprises a slit member forming a slit that extends in the direction that intersects the conveyance direction, the slit member disposed on an upstream side of the scintillator unit with respect to a direction of X-ray irradiation so that only the X-rays that passed through the slit enter the scintillator unit; wherein the slit member is arranged so that a width of the slit is narrower than a width of the scintillator unit in the conveyance direction of the target object, and that the width of the slit is equal to or wider than half a light-receiving width of the photodiode array in the conveyance direction of the target object, the slit member, the scintillator and the photodiode array are positioned in the stated sequence listed from the top, and are provided between the first portion of the conveyor belt and the second portion of the conveyor belt, and the X-ray emission device is provided above the first portion of the conveyor belt.