To visually confirm a meat block inside of a meat box without moving an upper cover in the direction for opening the box at a part over the meat block while maintaining rigidity of the upper cover for covering an upper surface of the meat block by providing a transparent member in a part of the upper cover.

A top surface of a shaft is provided with a supporting member 17, and the supporting member 17 is provided with an upper cover 14 extended to a side plate and formed with a surface in parallel with a bottom plate so that the upper cover 14 is horizontally turned around a supporting point 15. A transparent member 16 made of the acrylic material, vinyl chloride material or the like is fixed to a position for covering the top surface of a meat box 8 except for near the supporting point 15, which dose not give the influence to the rigidity of the upper cover 14 for covering an upper surface of a meat block 19. With this structure, residual quantity of the meat block 19 inside the meat box 8 can be visually confirmed through the transparent member 16 during the slicing work. Residual quantity to be sliced and time to be required for processing the residual quantity can be easily grasped.