A seal checker for conveying and pressing a packaging bag by upper and lower conveyance units is provided which is capable of saving space with a compact structure, and is also capable of improving maintainability and cleanability. A lower transfer conveyor is mounted on a main body frame, and an upper transfer conveyor is supported by an elevating mechanism mounted to the main body frame. The elevating mechanism includes first and second link members and a frame that connects upper end portions of the link members to each other. Lower portions of the first and second link members are connected to the main body frame. The frame is configured so as to move in parallel with the lower transfer conveyor.