A thin-slice manufacturing device is a thin-slice manufacturing device for cutting an embedding block in which a biological sample is embedded by paraffin using a cutting blade relatively moved with respect to the embedding block along a virtual plane to cut out thin slices, the thin-slice manufacturing device includes a vertical illumination part configured to radiate light to the embedding block, and an inclination estimation part configured to detect a boundary line between a cutting surface cut along the virtual plane and a non-cutting surface based on reflection of light generated by the light radiated to the embedding block by the vertical illumination part, and estimate inclination information showing information related to inclination of the embedding block based on the detected boundary line.