A thin section preparation device that is capable to cut a thin section from an embedding block in which a biological sample is embedded, and to prepare a thin section sample by placing the thin section on a substrate, the thin section preparation device comprising: a cutting blade that is configured to relatively move with respect to the embedding block in a direction parallel with an X axis direction in which a first side of the embedding block extends, and to thinly cut the embedding block in order to cut out the thin section, the edge of the cutting blade being disposed to be inclined in a Y axis direction, which is orthogonal to the X axis direction; a storage tank that is configured to store a liquid, and to spread the thin section by floating the thin section on the liquid in a state where a first side of the thin section is parallel with the X axis direction, the first side of the thin section corresponding to the first side of the embedding block; a conveying mechanism that is arranged so that a first portion of the conveying mechanism is disposed in a state where the first portion is close to a blade edge of the cutting blade while having a second portion of the conveying mechanism immersed into the liquid, and that is configured to convey the thin section in a direction intersecting the X axis direction in a plan view of the XY plane in a state where the first side of the thin section is parallel with the X axis direction; a substrate disposition mechanism that is configured to place the thin section floating in the storage tank on the substrate in a state where a first side of the substrate is parallel with the X axis direction in the plan view; and a rotary body that is provided between the conveying mechanism and the substrate disposition mechanism, and that is configured to convey the thin section toward the substrate disposition mechanism by rotating in a state where the thin section is placed on an outer surface of the rotary body, wherein the rotary body is configured to be rotatable about an axis parallel to the Y-axis in a state where a portion of the rotary body is immersed into the liquid of the storage tank. a cutting blade that is configured to relatively move with respect to the embedding block in a direction parallel with an X axis direction in which a first side of the embedding block extends, and to thinly cut the embedding block in order to cut out the thin section, the edge of the cutting blade being disposed to be inclined in a Y axis direction, which is orthogonal to the X axis direction; a storage tank that is configured to store a liquid, and to spread the thin section by floating the thin section on the liquid in a state where a first side of the thin section is parallel with the X axis direction, the first side of the thin section corresponding to the first side of the embedding block; a conveying mechanism that is arranged so that a first portion of the conveying mechanism is disposed in a state where the first portion is close to a blade edge of the cutting blade while having a second portion of the conveying mechanism immersed into the liquid, and that is configured to convey the thin section in a direction intersecting the X axis direction in a plan view of the XY plane in a state where the first side of the thin section is parallel with the X axis direction; a substrate disposition mechanism that is configured to place the thin section floating in the storage tank on the substrate in a state where a first side of the substrate is parallel with the X axis direction in the plan view; and a rotary body that is provided between the conveying mechanism and the substrate disposition mechanism, and that is configured to convey the thin section toward the substrate disposition mechanism by rotating in a state where the thin section is placed on an outer surface of the rotary body, wherein the rotary body is configured to be rotatable about an axis parallel to the Y-axis in a state where a portion of the rotary body is immersed into the liquid of the storage tank.