A thermal recording sheet comprising, on one surface of square, transparent film, a thermal recording layer containing leuco dye and a coloration agent and a protection layer mainly containing water-based resin, wherein corner parts (1a, 1b, 1c, 1d) including at least one marked corner part (1a) are provided at its four corners. The corner parts (1a, 1b, 1c, 1d) respectively have end edges each with radius of curvature of at least 5 mm, and the end edge of the marked corner part (1a) is provided substantially with a maximum radius of curvature or a minimum radius of curvature.