To provide a means that is less likely to misidentify a crack as a foreign substance during an image checking in which a vibration is applied to a powder contained in a bag-like container. A foreign substance checking system includes a vibration device configured to apply a vibration to a container, a photography device configured to optically photograph the inside of the container through a transparent region from the outside, and a determination device configured to determine whether a foreign substance is present inside the container based on an image of the container photographed by the photography device. The vibration device includes a rotating shaft and a hammer rotating in conjunction with the rotating shaft and colliding with the container. A portion of an outer surface of the hammer to abut on the container has a flat surface.